Well this is an interesting post.
I'm of the belief that by 14 or 15, guys know what they are- could be you were kinda hiding it from yourself, however.
I'm bisexual, male(ish). I started the anal exploration when I was 11 or 12, so we have that sort of in common.
Bisexual is a big umbrella. A person can like one sex one way, the other sex a different way- it's like a jigsaw puzzle, and I suspect they're rather like fingerprints- no two people that identify as Bisexual probably experience their attractions in quite the same way. I'm romantically more attracted to girls- with exceptions. I'm more excited by the thought of same-sex acts, than opposite sex. I check out girls in public, and never men- not that I'm afraid to, I just never think to do it, and only infrequently check men out. However, the naked male body interests me at least as much as the naked female body, if not more. But clothed girls interest me more than clothed men. How messed up is that? But it is, what it is. Aesthetically, I think the nude female form is prettier but again, the libido wants what it wants.
And my experience with how it all fits together isn't yours, and yours isn't another bisexual's.
I have OCD- which means I obsess, and for a long time I'd go back and forth- Gay, Straight, Gay, Straight. I live a mostly heterosexual existence, but find myself very homosexually centered. I had to just sit down and mentally tick off the two columns, and I can only say I'm bisexual based on the evidences. I think that's all a person can do.
Have you taken any kind of halfway serious orientation self-tests? There used to be an excellent one up, the Flexuality Test, but unfortunately it uses Flash and since the end of last year all modern browsers block it, and it's no longer supported by Adobe, as obsolete (as well as full of security holes).
Do a search for tests based on the Kinsey scale- it's a little one-dimensional, but it usually averages me out pretty good. One based on the Klein is even better, it's a little more multi-dimensional.
Here's a Klein based checklist in PDF format
http://www.drmimihoang.com/uploads/3/1/ ... mhoang.pdfAnd here's another test
https://psycho-tests.com/test/sexual-orientation-testI took it real quick and well they were aiming for the last six months- I did for my adult life, I presume 'last 6 months' is aimed at younger people. I'm pretty old.
https://images2.imgbox.com/c8/a1/ebIyQDG4_o.pngI came out 58% Hetero and 79% Homo out of scales 0-100% in each direction, on a vector map which plants me in the Bisexual quadrant. Nothing I didn't already know, but it matches me close enough.