I think I'm bi, but I don't know

I've never been romantically attracted to a man before. Every single crush I've had has been on a woman. The issue is that gay porn turns me on a lot, sometimes more than straight porn. The image of an erect penis on a ripped male gives me an erection. I've had fantasies about men. After I "do my business", I feel really grossed out about it. Am I gay?