I am a 20 year old male. My foreskin doesnt retract at all and I have never been able to see the head of my penis which is otherwise fully functional?

? need evaluation ? If this doesn't bother you, accumulate debris, get infected or produce pain during an erection you might just ignore it.(bad idea) Please NEVER try to force the foreskin back or it could act like a tourniquet and amputate the distal end of the penis. You should consult with a urologist who can give you options for releasing the foreskin.
Phimosis . Phimosis is the term for this condition. This is a normal condition at birth, but children outgrow it by age 3 or 4. Please see a physician to see if anything particular is causing your foreskin to not retract. ..... Usual treatment for this condition is circumcision.