My frenulum is short and goes whitish and hurts when i try to fully retract my foreskin,when erect,so i'm afraid to have sex. what shall i do?

Phimosis: You might be describing phimosis. Check out http://www.medicinenet.com/phimosis_and_paraphimosis_penis_disorders/article.htm then go see your Family Doc who may prescribe a steroid cream to apply to your foreskin to aid w/retraction. If that doesn't work, then you may want to see a Urologist to consider circumcision.

See urologist for...: Have a urologist take a good history and a look at it so to decide what and how to help you resolve your concern around your foreskin. That is surest to do.