Need advice!!!

My boyfriend and I have been on and off for around a year. We got back together around 5 months ago and he is convinced that we will be together forever get married. He is so sweet and kind and caring, everything I say I want in a guy, but for some reason I’m just not that into it.I find myself wanting to be near and close to other guys, specially one guy who doesn’t want me at all, and I couldn’t ever have. I am so upset with myself that I can’t appreciate how great of a guy he is. When we have sex it feels really good but I don’t feel connected to him. I don’t know if I expect too much or if I’m reasonable, a part of me just wants to stay with him and be happy with what I have, I might not find a better guy. But another part of me just wants to get out and be single for a while, and just have fun. I don’t know what to do.