What can I do to make my friend realize I just want to be friends?

So, two years ago I started to hangout with a guy I met at work. After meeting up a couple times of he asked me if we could go out. I said no. I told him that I don't date my friends, and if that hanging out with me would make him feel awkward, we should just go our separate ways. I went on to say I've dated my friends in the past and all the relationships ended horribly. He then told me, that he was fine and he didn't mind being "just friends." Flash to a year later we're still hanging out and now I have a boyfriend. I go to tell my friend all about my bf, because I thought we could all go out and have pizza or something. However then, my friend told me he still liked me and that this conversation was making him unconvertible. I couldn't help but feel a little guilty, I had my doubts about our friendship being only one sided that partly being the reason I wanted the two to meet. So, again I told him, I don't date my friends. It's been a year since then, and he has told me that there are girls he's interested in, but I never see them. And I have since broken up with my ex. He is a great guy, a wonderful person, but I'm not attracted to him, and he knows that. It's uncomfortable to be around him sometimes because he tends to hover over me, or sit really close to me when there are plenty of available seats around, and he gets over protective around our friends. I think in his mind we're dating. He's my best friend, but I don't want to hold him back. What do I do?