BF Avoiding Sex

So my boyfriend and I used to have an amazing sex life and would be a 2x minimum per day. But now we are at like once a month. I’ve told him how I feel like he doesn’t desire me anymore. He said it’s not that and that he finds me very attractive. However, he said he is feeling very self-conscious of his slight weight gain and that he feels he can’t last long enough to truly pleasure me. We’ve talked about it but instead of working on it I feel like he rather just avoid sex all together. I feel shut down every time I try to make an advance. He’ll either say he’s tired or redirects the conversation/situation. I’m not sure what to do.