Why is it that when i get an erection and i pull my my skin back but my head of the penis wont go all out and it starts to hurt ?

Phimosis: Poor hygiene &/or recurrent episodes of infection of the glans (head) &/or prepuce (foreskin) can lead to scarring of preputial opening, leading to pathologic phimosis, the inability to retract the foreskin over the glans. See fp or urologist for evaluation & treatment. Do not force foreskin lest it become caught in the groove behind glans, which may require surgery to correct.

Phimosis: Phimosis is the inability to retract foreskin over glans of penis. Paraphimosis is condition of foreskin remaining stuck in retracted position. Check out http://en.Wikipedia.Org/wiki/phimosis for more info. Then go see your family doc for diagnosis & treatment. Some studies suggest topical steroids can help reduce phimosis & reduce need for circumcision.