I also want to just touch on this, and I hope that's okay, there's been a lot of information shared.
There's no time limit or expectation of when you have to figure this out by. I have a 23 year old friend that told me she thought she was gay for a while then bi, then other things and then just finally said she didn't care and didn't want to keep forcing herself with these labels and just said "I'm attracted to this person, I'm not quite sure what that means, and that's okay." I kind of just sat there like "cool, I don't feel like dating right now." and we kind of just ended it with talking about tacos.
For me, I say I'm gay but it's also a label that was thrown at me for a while, and for me, my sexuality isn't a major piece and I just kind accept that I like who I like, kind of following along with what my friend did. And since I stopped caring about it, I find myself a lot less stressed out. There's no norms you have to fit yourself to is what I'm trying to get at, there's nothing saying that one label might feel amazing at a certain time and maybe your feelings towards that label will change. It's also okay to say "I don't know" by the way. It's a really confusing thing to deal with and it's okay to just not know right now.
However, I'm not far off from your age, and it took a long time to get to the point where I just didn't care, and so believe me, I know that questioning yourself can be so difficult. One thing I did and I really advise anyone I talk to against, is forcing yourself against how you feel, if you notice you like someone, I challenge you to instead of attaching reactions like this is "good" or "bad" just notice that you feel that way and let yourself know that however you feel is okay. I forced myself to be in a relationship with a girl to convince myself I could be a typical straight dude, and I still regret doing that - granted it created drama, and left the person I was with hurt and me even more confused than I was to begin with.
Know, sexuality may feel like this massive thing right now, and even if your friends have it figured out, it's okay if you don't. Always though, try to treat yourself with kindness, and I like how horriblegoose put it, imagine that this was your friend you were talking about, would you ever judge them for feeling this way?
Also, don't know how much you want to hear this, but I'm glad said it to me looking back - You have your whole life ahead of you. Being gay or straight or whatever you identify as, -although it may be really important to some people and a massive part of their identity, for some people it's just not, that's okay - doesn't change who YOU are. You're still you no matter what.
You have the power to say "This is not how my story will end".