Well... I'm no expert and I'm straight myself, so I can't give a straight answer (no pun intended, seriously) and I don't think anyone can. Romantic love and attraction are complicated things and there is no set time as an adult to start noticing. Just a time when your type starts shaping. Really noticing happens with life experience and the desire to meet someone.
With that said, I think it is possible you are bisexual, but not because you had some bad relationships or anything. Nobody starts swinging a certain way just because they went through something bad or good. I mean, look at how many straight people stay straight even after leaving abusive relationships.
Also, being bisexual doesn't mean you have to have dated one of each gender. It's not a mark. It's just an orientation. Only go into a relationship if it is what you really want not just to experiment because that will lead to even more hurt for you and the other party.
Also, you don't sound homophobic. Just like a young person and that's ok. Some people don't realise they are bisexual until they meet someone who is their type from what I have seen. My advice is maybe you are, but it is no big deal and it doesn't dictate who your soul mate will be or who you are. Just live life and be romantically involved with someone you REALLY want.