And here I was, thinking this only happens on TV. Let’s first address him being in bed with another dude: don’t address it. Is he gay? Bi? Who cares. That’s his own journey of self-discovery that he needs to hurry up and embark on without you being collateral damage. The truth is, you’d have the same reaction if you’d walked in on him in bed with a woman. His sexuality isn’t the issue. It’s his fidelity.
Address that. From what I know from friends, coming out of the closet can be complicated, traumatic (the world is still full of prejudiced dillweeds,) and confusing. It’s unfortunate that this part of his life has come to light in a way that is, fundamentally, a betrayal of whatever trust the two of you had established. So, to reiterate, he cheated on you. With whom is of no consequence… to you.
Do me a personal favor and don’t be a doormat. I know that’s easily said than done. But the sooner you hear that, the easier I think it will be to address the fact that your boyfriend brazenly, or stupidly, allowed himself to get it on with someone else in a bed that you both share. Look, I have a shady past. I’ve done some things I’m not proud of. I’ve been a real douchebiscuit. I won’t try and interpret what it says about someone who would cheat in a way that makes it possible to get caught. He’s trying to tell you something? Inducing a break-up the spineless way: by making you do it? I know in the past, when I didn’t want to get caught, I wasn’t caught. His motivations, however, are not the topic at hand. Leave that for a future where you can be healthier and happier. When you have perspective.
Which brings me back to the awful “doormat” phrase — you can’t make a person “happy.” The best you can do is find those people and activities in your life that make you happy, and hope the example rubs off. You could try to work this out with him, but for the time being, I think putting as much distance as you can between him and you will only serve to help you get your head together.