How to know if you're a lesbian?

I'm 15 and had always been attracted to guys. I'm not well 'attracted' to girls, but I get turned on if I watch porn videos of them or something. I have never had a crush on a girl and thinks that kissing girls is kinda...gross. I want to be married to a guy and have kids when I'm older and stuff, but I am sooo freaking out that I might be a lesbian. I mean, I've touched my friend's boob accidentally and was pretty shocked at it. I didn't you know, LIKE the feeling. I was just neutral about it, I guess. I just don't want to be married to a straight guy and decades later, finally found out I'm a lesbian! Pleaaase help meee! Does it sound like I'm a lesbian? And how do you know if you're a lesbian?!