Unsure of my orientation... Help???

So I've got a bit of a dilemma...

I fap regularly. To porn usually.
And I think I'm straight.

To explain, I've had a girlfriend for a year and a half now.

So once when I jacked off, I noticed I orgasmed at the first sight of the dick.
I didn't think much of it, but then it happened again, and again...

I've experimented with one of my male friends. More than once. Not recently, though. But I've had urges to try again. Both of us have girlfriends. Just letting off steam and curiosity, you know?

So I decided to watch exclusive one-sex porn for women and men as an experiment.
I pleasurably orgasmed to both, but... Faster to the men.

I'm definitely turned on by penises, but not more so than breasts or vaginas. At least I think.

And the main difference is, while I'm attracted to both genitalia, I'm only attracted to women, romantically. I would never have a romantic relationship with a guy. I'm very happy with my girlfriend. Were just both virgins.

I'm a teen, by the way.

Sorry for the essay, but this is probably way oversimplified.

Thanks for any responses.