This is never okay. Ever.

Please do not feel forced to lose weight and become obsessive about it. That is a good way for an ED to start, and trust me, I am anorexic. And I started because my grandmother called me fat even when I wasn't and I made the mistake of placing my self worth and perfectionism on my body image. And it is sick and horrible.

Your husband is shallow. Which sounds blunt, but it is true. If he is finding issues with your sex life and his only excuse is your weight, then I bet loads of cash that there is something deeper there for him. He wanted respect when he was heavy, which you gave him! Your love didn't change! Nor should his just because he happened to get ill and lose weight.

You owe him nothing physically. You are your own person, married or not. You deserve self preservation and your own sense of self. Your body is YOURS. Not his to police and change.