Questioning My Sexuality

Hey my name is Alex. I'm a 15 year old girl, and lately I've been questioning my sexuality. See, I've always had crushes on boys, and seen girls as nothing but friends. Except recently, I don't know why, but I've felt attracted to girls and I'm really confused. Like whenever one of my really good friends would joke around and say something sexy, I would be turned on. I dont know if it's her, or what she said. I care about her a lot, but I'm not sure if I like her in a romantic way or not. I've also read a couple books with lesbian couples and I like it or I've had a crush on a female fictional character. I'm not sure if this is a phase and I'm staight, or if I'm actually bisexual. I would think that if I was bisexual I would have always had crushes on girls my whole life and not just recently. Thanks for listening, and feedback would be greatly appreciated!