I think I like girls and I want to come out but how do I know for sure? I don't have a crush on any girls I know so what if I'm not lesbian?
The best thing for you to do is explore with both genders so you can find out exactly what you are emotionally/physically attracted to. Many, if not most people are curious about relations with the same-sex so get out there and see what works for you. There are many straight girls who experiment for a little bit and then go back to men or girls who experiment with other girls and end up falling for them. I remember as a 15 year old girl I never could see myself in a relationship with a woman but now when I see same-sex relationships they make me very emotional and I truly see the beauty in them. Sometimes our minds make us repress our feelings, so try to stay true and don't rush for answers, you are still young. Good luck x
Even if you are not currently interested in anyone, your orientation doesn't suddenly become invalid. You can look at your past: have you had crushes on guys? On girls? Have you enjoyed physical/sexual contact with guys/girls? Have you been sexually/romantically attracted to guys/girls? Any celebrity crushes? You can look to your future: If you think of having a relationship with someone, which gender is that someone? Could you see yourself loving a girl/a guy? If you tell us why you think you like girls, and why you're not sure, we'll probably be able to help you figure it out! That said, you're young. If you choose to come out now, and later realize you're not a lesbian -- that's okay. You're allowed to make mistakes. It really wouldn't be the end of the world. What if you're not a lesbian? Well, at least you'll know.