Im having trouble with paying attention in my class because a guy I like sits behind me. I keep day dreaming of dirty things I want to do to him and my friends say I need help. My grades are dropping and I don't know who to talk to about this. I want to talk to him but I turn red and no words form. How do I make these thoughts go away so I can learn in class.

Your better off telling him you like him! You will only regret not telling him, trust me from personal experience.

Ok ill try on Monday...only problem is he has a girl already, so im gonna be rejected

That’s a major factor, knowing this information I wouldn’t tell him just yet if I was you. If you become friends with him for now, then you can see what he is actually like. If then things happen to not to go so well for them, you have a major advantage above all the other girls.

I think you should still tell him, but also ask if you could be friends with him.

If he accepts your confession when he already has a girlfriend, that is a big red flag in your face.