Relationship, or lack there of, advice?

I'm starting to question whether or not I have something wrong with me. In my 18 years of life I've never had a serious boyfriend, and I'm not sure if I even want one. I like guys, I know I do, and the thought of being with one is, good, but when I actually meet someone and even if we get on great, the minute they want to be my boyfriend, and I there girlfriend, I feel trapped. I feel like, they have a piece of me, and it makes me nervous. I'm asking this because a boy has just asked me out and I've said yes because we met and got along great, but theres still something in me that now feels, uncomfortable, at the thought... I think its the expecatations someone holds when you get into a relationship. He's already told me he gets bored when things are taken to slow, and it's going to have to be because I'm still a virgin and I haven't held onto it this long for nothing. I think I also have expectations, I always think, "oh, what if i say yes to them, and now i'll miss out on my chances with mr right?" I think it might be important to tell you that I've seen 2 other guys. Number 1 was the big brother of the boy I actually liked who just wanted one thing and i had to say no alot. And 2 was a boy who liked me from school who I finally caved into and dated, for a month. Neither were boys I really wanted to be with, I often admire guys from afar and get shy pretty easily. I suppose it also might be useful to let you know my best friend is gay, I think it's important because I feel no threat around him because I know he's not attracted to me. But at the same time, I do like guys liking me, oh I don't know :( I don't even know what it is exactly I'm asking, I guess I just want to know if anyone else feels like I do, or if its abnormal. And how to be happy