Why do you still get turned on by guys when you like girls?

Sexuality is fluid. Gay, bi, and straight are all generalizations that we use because humans like to categorize things. The problem with these labels is that when they don't fit, it can lead to confusion and misunderstandings. No one is 100% gay or straight. No one. Even the straightest man in the world may find himself turned on by a man.

Second of all, people experience two kinds of attraction: sexual and romantic. Think of it as the difference between love and lust. So it is possible to be mostly attracted to girls both ways while feeling sexually attracted to boys from time to time.