I don't seem to connect with my gf?

My gf has a best guy friend thats also a friend of mine. We both met her around the same time and she liked me. But when she did I used to like someone else, and she got tired of waiting for me and she started kind of liking my friend, but she told me that was the only reason she started liking him cause I liked her and another girl. Well, now were dating cause i started liking her also. The thing is, now that guy and her are like best friends, and they communicate very well. Whenever theyre together, theyll always be together, and I'd just walk off. She'd try to get my attention by coming up to me and etc, but they'd end up being together again. Yesterday, I had enough of it, and i asked her if she regrets going out w/ me and rather be with my friend than me, and she said no, and she said he's just a friend and her eyes started tearing up. We have fun when were together, just not when were around other people. I guess its just me but I'm not sure.