Foreskin problems. Please help.?

I'm nineteen, and have never retracted my foreskin (didn't know you had to). But since i've started having , my foreskin has been stretched and it hurts during and after. Now its been stretched so far that all of the head of my is showing and its really raw and painfull,and it's stuck there. Please help, its painfull and i'm quite nervous about it.