Is it normal that i confuse fondness with attraction?

I don't really like people all that often. I mean people are cool and all, but I don't click with most people beyond an initial conversation. So it seems that when I do find someone I have fun talking to and who I feel comfortable around I become attracted, even though I am in a relationship. It's never about looks or anything, it's just people I feel really friendly around, who I feel I can be myself around. I wouldn't cheat or anything, but sometimes my thinking about the person will turn a little obsessive. I'll start thinking of them like a crush, despite my happy relationship. I usually feel like the other party is also into me and I like it, but I would just like to be friends with cool people instead of me thinking I like them like that. It tends to just make things awakward for me and the friendship never evolves or even ends abruptly because I start acting different and they probably think I'm just crazy because I don't communicate any of these things.