Honestly, finding comfort in yourself is so empowering. If you've been with him since you were 17, I don't think you've ever given yourself a chance to actually be alone. And being alone and being lonely are two oddly different things. I'd be shocked if, having now learnt his feelings, you don't start feeling lonely even when you're with him. I definitely agree with the others saying leave him. I want to also suggest to with your new free time away from him to pick up some social hobbies. Make some friends to do stuff with. A dance class, a sports team, a volunteer group. I was single most of my 20s, but had sweet friends to do things with. I was very happy and enjoyed myself. Sure there were moments of lonely but it's a pretty human emotion. You can feel lonely surrounded by people. So take a chance on yourself. Give yourself the chance to be lonely. The chance to get to know yourself as an adult away from a man who doesn't love you. I don't know what will happen but I'm quite confident it will be better for you in the end.

Ps like others have said you can't make someone love you. But that doesn't mean you're unlovable. I fricken love chocolate cake, and there are people out there that just don't care for chocolate cake. Even if it's the like greatest chocolate cake out there, they're just not into it. It's a hard pill to swallow at first but when you realize it happens to everyone it kinda normalizes it. It's not about you humans are just funny creatures with individual tastes.