I just want some advice or just an opinion

Hi, I am 19 yrs old, and my ex is 21. We live together, for over a year now, been together since I was 15-16. And broke up in July, I broke up with him, for a lot of different reasons but nothing to do with cheating. I started messing around with another guy after we broke up, but we still live together and I told him he can do what he wants as long as it’s not brung into the home we live in out of respect.. but he doesn’t want anyone else that I know of and always wants sex with me. Even when I tell him I don’t want too anymore bc I don’t have those feelings anymore , but I always give in bc he makes me feel guilty about not having sex with him, and I also feel bad for having sex with someone else but I am technically single, I make it clear to him a lot that I am single and so is he. He gets mad when I leave the house, etc, I just don’t know what to do anymore , I feel like I’m wrong for not saying I mess with someone, but again I feel like it would turn into a pointless argument bc we’re not together.. I need opinion or advice