I am assuming from the verbage you used that you cheated on him, but that you don't want him to leave you for it. Let me know if I am making the wrong assumption. If you DID cheat, and they two of you wish to stay together, then I recommend counseling, STAT. The two of you obviously lack the skills to overcome the rough *patches* that you have encountered in the past. His demands about your physical appearance are a poor manifestation of his fear that you will cheat again. When two people both want to work through infidelity, the chances are good that they can, provided they have professional help.
If you have not cheated, then he is simply excerting control over you and is displaying abusive characteristics. Exit the relationship as soon as you are safely able to, and get yourself into counseling for some self introspection. People who end up in an abusive relationship often fidn themselves in another. You have some learning to do about healthy standards before you attempt future relationships.
All the best to you.