[24m] Super Confused about Sexuality

I've always known I was bi, ever since I first started having fantasies, they were about both guys and girls. There's been a few times in my life where I got seriously confused and thought I was gay, most recently when I was around 18/19 and I even came out to a friend. However I've always dated girls, and for the past couple years I thought all the confusion was behind me. Yet All my life there's been so many signs I cant ignore: my first sexual experience was with a boy when I was 12, I've made out with guys before, I once had a sleepover at a friends house where she put makeup on me and did my hair, and many other little things that add up... I always thought my attraction to men was basically just hornyness and lust, because while the idea of cock excited me, just the thought of being with a guy felt wrong, I couldn't accept that I could be like that, I feel like it would take my masculinity away. But I realize that I've been denying and ignoring the fact that I do think about guys and find them attractive, I think the only reason I felt wrong about it was because I didn't want to be gay, I was fighting against it. Anyways like I said, I thought being confused was behind me, and I'm dating a girl I love very much. But last weekend I came to a video of a guy jerking off and since then I haven't stopped thinking of the dirtiest gay shit, even getting hard at work thinking about it. I want this subs opinion, is this just a phase, and I can go back to feeling straight, or is this a symptom of a larger problem? I don't know if its just horniness or what, but all of this has been making my head spin, and I haven't been able to look at my gf the same way. Sorry if my this is confusing to read but I'm just as baffled.EDIT: its late and I don't have time to reply to everybody, but Id like to thank you all for the advice. As I hoped, you were all very friendly and supportive and you've given me a lot to think about. I'm not going to try and shoe horn myself into a label, I'm happy with what I am! Whatever that is! I'm just going to go with it and honestly evaluate myself after I've had some time to let it all sink in. I'm not going to leave my girlfriend unless I honestly feel like I'm not attracted to women at all anymore. Thanks everyone, love you guys.