Only you will know, but I agree with Penni that feelings can be muddled after a break up, so do be careful and consider that too. But it's also okay and normal to develop close feelings for someone who supported you when you needed it, and that's okay.
If you find you can be attracted to more than one gender, you can call yourself bi (or pan). The past relationship going badly doesn't necessarily change the fact that you were attracted to a girl and have since been attracted to guys. But if you find you're normally only attracted to one gender with occasional unexpected outliers, you might want to look up the Kinsey scale for insight. Attraction can be complex!
It's not strange or unusual to still be figuring things out. I didn't know being ace was a thing until I was in college, and years since I'm still not 100% sure what I am. I feel vague about it. XD
It's okay to just go with whatever feels right/comfortable.
I'll also add I had a couple friends cone out to me as bi, including my college room mate, and it didn't change our relationships or how I saw them at all, while not everyone is that way, I just want you to know for lots of people it's no big deal. You're you regardless!