To answer your question, you don't. 

You are driving yourself crazy trying to be "fair" and make sure everyone gets equal time. This is BS, you are dealing with grown adults. They need to deal.

The real underlining issue here, is your husband, he is the one who could fix this. You need to have a real heart to heart with him. I would also recommend going to a counsler to help you two have better communication and understanding. Your Husband is freaking out of his mind with the staying at his moms house when she lives 10 minutes away. I would stab my H for every single thing you mentioned. Your MIL has no boundaries and absolutely no respect for you, your husband or the family you have created.

You need to make a stand for your self and your child. This is freaking ridiculous, I'm sorry. 

Oh and the next time he whines how it is not fair, please remind him that is life. Life isn't freaking fair. Ask him, is it fair that I live in chronic pain? Is it fair that your mother doesn't respect us enough not to barge in uninvited? 

I am sure you can find more examples.  

So many things to say.

1) You and your husband need to get on the same page PRONTO. There needs to be boundaries when it comes to your MIL, and he needs to help enforce them. If she comes over without calling first, you don't answer the door. If she says something out of line, you leave or ask her to leave.

2) Almost as importantly - you need to start putting yourself and your immediate family first. You don't need to go stay at your parents' house once a month. No, you don't. They don't need to come to your house twice a week. Your MIL doesn't have to babysit once a week. No wonder you're stressed out - you work FT and use every second of your free time hosting visitors and running around making sure that everyone gets time with Trent. STOP IT. Seriously, stop it. You need to be enforcing boundaries with everyone, and none of the grandparents will die if they have to go 2 weeks without a visit. You need time to be just the 3 of you, without grandparents standing around, without being on the road to visit someone, just being at home relaxing and enjoying time with one another.

You can't make everyone happy. PP is right - life by its very nature is unfair. Stop worrying about trying to make it fair, and start being a little more selfish with your time and your baby. There's no way in hell that I'd even contemplate staying with your MIL when she lives 10 minutes away (tell your husband to grow the *** up). There's no way I'd continue letting her babysit if she's being rude or pushy. There's no way that I'd be running to my parents' house every couple of weeks if I didn't feel good and was having health problems. You really need to get your s**t together, and like I said start taking care of yourself.

You have an infant, fibromyalgia, and a full time teaching job.  Any one of those three things would be reason to slow down, pay major attention to your needs and build in time to relax and recuperate a little. WIth the combination of all three of them, it's even more vital.  

When you are in a stressful time in your life- like this one- pay really close attention to which people are rallying around you to help and support you, and which ones are putting more pressure on you to do more, be more, and make their lives easier.  Your mother-in-law is in that category, yes- but so is your husband.  He's got a front-row seat to see how stressful this is and knowing that this affects your health, and he's applying pressure to see his family more and make sure everything is "fair" as far as how much baby time the grandparents get. 

So, the first thing to do is to have a heart-to-heart with your husband- and to be very upfront with how much you need to be a priority, and how upset you are that he's showing more concern for the grandparents' desire to see the baby than for your need to be rested and healthy.  Also point out- schedules for how often to visit family need to be flexible for the stage of life you're in. Just from work schedules alone, there have been years that my husband and I could see family multiple times a week and years where once a month had to do.  You need the flexibility in your own life to say "I'm not up to driving down to see my parents this weekend," or "I'm not up to a family visit this evening, I really need extra sleep." And while your extended family might not grant it graciously or might complain about it, your husband absolutely can- and absolutely should- intercede.

My honest advice is to sit down with your husband, look at the next month, and decide what you can whittle down.  Not just family visits- look for ways to cut down or even skip some of the household chores, ways to get meals prepared and on the table quickly, everything.  Is the babysitting your parents and his provide truly helpful, or does it create work in the form of needing to have the house clean or having to entertain them? And your parents sound very willing to make the drive- let them do the driving to see the baby instead of making the two-hour trip to go there.  Streamline, relax, and let the focus go back to making the best life for your baby, self and husband, instead of the easiest life for your extended family.  

Sounds like you and your husband maybe need to work on YOU time!

Stop trying to cater to your extended families and work on your immediate family (you, your husband and your child). Once you have the dynamic down within your own household, THEN start worrying about how to get enough time with your parents and his parents.

BTW, I think it's ridiculous that he is pulling that BS about staying at his parents house. I loathe not sleeping in my own bed, and if I have the option to I will always choose to go home. Your husband needs to grown up and start putting you and your child first. 

A couple thoughts....

I have spoke to my husband on multitude of times regarding his mother.  She never listens.  He has spoke to her and it still hasn't made a difference.  My husband is finally starting to see things from my point of view.  I spoke up to his mom for the only time because she keeps expressing her thoughts and I wanted to put out my view and what I think of the situation.  I asked her not to come to my house because I was staying home sick and didn't want to have a facial confrontation about it right now.  He also spoke to my parents which let him realize that his mother is being rediculous.  She showed up at my house anyways and I had to call him and the police because she stated she won't leave. 

In fact, having the parents babysit actually helps out.  We have to be at work anyways.  It saves us from having to pay for daycare, it gives them time with the grandson so we don't feel so stressed about having to provide time, and my mother-in-law was cleaning my house when she came over.  My mother-in-law won't be babysitting him anymore because when I said she doesn't listen about things with my kid she said you don't get to control everything. 

As far as my parents, we're not holding stringent to the once a month thing.  It kind of would be crazy if we were.  I just like to try to see them that much because they live on a remote lake that I've been at since I was seven years old.  My favorite activities are: snowmobiling, snowshoeing, waterskiing, wakeboarding, swimming, kayaking, canoeing, paddleboating, hiking, etc.

Maidstone:

My husband is finally starting to see things from my point of view. 

Well, this isn't the way that you made it sound in your OP.  So are you backpeddling?

If you really had to call the police on your MIL to get her to leave your house, I sure hope that you are seriously distancing your family from her.  Not just "no more babysitting", but no more contact with your son since she's a pyscho.  If you're still seeing her at all, you're a nutjob.

I get that you love your family and like doing all of those activities.  But if you are sick, you need to slow down and take better care of yourself.  Relaxing and spending quality time with your son takes precedence over waterskiing and hiking.

He doesn't need to talk to her. You all need to establish boundaries. Change your locks so that she can't walk in, don't use her to babysit, don't go to her family events if they start too late. 

You can't change her but you an change your reaction to her.

However, I think your DH is a bigger problem than you want to admit. He's comparing time spent w each side?  No, he doesn't see how his mom is nearly as much as you may hope.  

EastCoastBride:

He doesn't need to talk to her. You all need to establish boundaries. Change your locks so that she can't walk in, don't use her to babysit, don't go to her family events if they start too late. 

You can't change her but you an change your reaction to her.

However, I think your DH is a bigger problem than you want to admit. He's comparing time spent w each side?  No, he doesn't see how his mom is nearly as much as you may hope.  

Yep, this. You are trying to change her behavior, but really you all need to change YOUR behavior in how you react to this woman. You can't control her or how she acts. You don't want her to call a hundred times a day? Change your number or shut the phone off. Don't answer. I also agree that your DH is a major problem here.