I am so sorry that you are having to deal with this for such a long time — more than four years! The core problem, of course, is that the subtitle in this relationship is that he won’t love you less you lose weight. Good relationships don’t work like this. This is called a condition of worth. It means that unless you meet the standards he has said you feel unlovable. This is unacceptable. No one should have that much influence over your well-being.
Stop trying. This is the only way out of this loop. The moment you try to lose weight to please him you lose yourself. It means that you believe you’re not lovable until you lose the weight. It is time to do something for yourself, if you want to, not for him.
This is a vicious cycle. He won’t accept you — and the more you try to win his approval the worse you feel about yourself and then the harder you try again. Stop trying. This is a time in your life when you need to nurture yourself. Find ways to take care of you mentally, physically and socially — don’t let your husband’s pathology become yours.
Wishing you patience and peace,