Am I bi or crazy?

I'm almost 18 and I'm having trouble with my sexuality. I know I like girls but not in more of a relationship way than a sexual way. I'm more straight because I love men and having relationships with men, but the past few years some(very few) girls have been turning me on. I've been feeling this way since I was 7 but try to avoid the feelings until now.  m I crazy? I'm questioning if it's just a sex fantasy or if I'm actually bi. Opinions?