Is it normal to like and dislike a person at the same time?

I've been liking this guy since I was 14 and he has too, at least I think so. When I was 15, I started dating this guy mainly because there was things about the other guy that I didn't like. At the time that I was in the relationship, I'd still think about the other guy, and I was guilty of flirting sometimes. After four years, the guy and I broke up and a week after the guy I liked and I hooked up, I felt a bit weird about it later. It was like my feelings poofed away. Not too long after that I'd feel the urge to talk to him, because "I missed him", but I never wanted to see him because I thought he as annoying at times.

I am now 19, and away from this guy on a long vacation and I believe I like him, and I constantly want to talk to him to see how his day has been and just to honestly hear his voice. We constantly flirt, and he would like to be in a relationship with me, but I don't. I like him, but I don't want to be with him, but I'd hook up with him, but I'd get jealous if he was with someone else, and I want to hang out with him, but when I do I feel a bit annoyed, but I'd totally hook up with him again because it was AMAZING.

What the hell is going on in my head? lol