HELP!

I'm 17 and I have a thing with my co-worker, he asked me to be his girlfriend and I said no but we still have a thing, and I realized that I don't really like him at all, like the sex isn't all that good and he's a pot head and he isn't funny, and that's just not who I am and I want to end it because I want to be a free flying bird and be able to jump from nest to nest if you know what I mean! But he is super sweet and kind and I really don't want to hurt his feelings because he's a really great friend but I want to be free! What do I do?