Im attracted to guys but somethings holding me back?

So I've dated guys and I like guys, but I ALWAYS find something wrong. I keep getting thoughts that maybe I am bi, but I love guys and I cannot picture myself with a girl. I always try to impress guys and never girls but how come I can never just like a guy without having reasons not to date them. Am I scared? Why am I asking myself if i'm Bi when I don't think I am.