Do I have a sex disorder?

Hello,<br><br>I'm a 15 year old male who has been masturbating for around 6 months now. I'm not a virgin, but I don't really have a girlfriend (I just don't have time). I have been having fantasies about sex for quite some time now, but since I've started masturbating, I've started to get erection throughout the day and it really gets in the way of my life. It's distracting me in school, and it's also not normal. I can get a hard-on from just looking at a girl. I can be doing my work and I'll look over at my friends girl and I'll get an erection, and that lasts for hours. This isn't normal right? I've talked to my parents, and I go to the doctor soon, but I was just wondering if this was normal or not.