Giving space help

I'm embarrassed to admit this but my boyfriend of 3yrs is starting to get under my skin we barley have sex any more. He's too stressed. .. and he thinks that I've gained to much weight and I'm not trying hard enough to keep myself attractive for him. I don't believe in cheating and I hate to say it I have thought about it I don't see my self as fat and I get compliments on how I look when ever we go out... I don't want to give up on him but I want to fuck... I want to be called sex and he doesn't do it anymore... I was thinking about leaving for a while and letting him think but has that ever worked? Any seggestions?