Is it normal that my penis is moving around to men, though i'm straight?

I've noticed that my penis is moving whenever I see a man. Very often, it's even someone like my dad, but more so around like typical metrosexual NYC guys on the street. It's as if it starts to move towards an erection, but then sort of stops. It really annoys me, because I'm 27 years old, always have fantasized about and hooked up with girls, so I'm pretty much positive I'm straight. Maybe it's an emotional attraction, but not a sexual one?

Does this mean I may be secretly gay or bi? I feel much closer to guys than women because of my personal history with my parents and stuff (I'm in therapy and I'm working through that with my therapist), but in spite of my negative/fearful feelings (sadly) towards women (I have a g/f too), I always was much more sexually excited by women, in spite of me wanting to be emotionally closer to guys.

I've also tried m/b'ing to guys, and though it might work on some level, just the thought of a girl will get me off pretty much instantly, as opposed to the thought of a guy, where I have to put a ton of effort into being able to do that.

This is bugging the hell out of me - why is my penis moving to men and not women on the street, whereas I know I am straight? Does anyone else have this? Maybe it's just my body being happy to see others on the street, and too anxious to be happy around women? As a straight guy, I wish it was the other way around, that I'd be more comfortable so I could pop boners around women, and they could be happy to see it and wanna suck me, haha.