Problems getting it up

So couple weeks ago my boyfriend and I went to a good friends wedding and got really drunk. When we got home and tried to have sex he couldn't get it up. Which upset me at the time because I was drunk, but the next day I was like oh he was wasted it happens. The problem is ever since then he's been having the same problem. And it makes me feel so insecure because I've gained weight and I'm the heaviest I've ever been. So when he can't get it up it makes me feel like he doesn't think I'm sexy. He keeps saying that the first time it happened keeps replaying in his head and that's why he can't get a boner. Like it's messing with his head. Any advice?