If you can't clean under there, you'll need to see a medical person for some advice and possibly a small snip to free it.
(It's not as bad as that sounds...they'll numb it up, if that's what's indicated.)
I think seeking an option from your family doctor is warranted, but you may want to start with a school nurse or a football coach at school for advice.
Baby boys are born with the inner layer of the foreskin fused with the surface of the underlying glans penis. This is natural, normal, and protects against infection. Over some years, the fusion spontaneously disintegrates and releases the inner foreskin. This usually happens prior to puberty, but not always.
It is not uncommon in adolescence to have the inner layer of the foreskin still fused to the glans penis. It is not a serious problem.
Apparently, your foreskin has not yet released, although it probably is about ready to release due to your age. You can try peeling the foreskin away from the glans penis to see if you can break the remaining fusion. Do it carefully and little by little. It may take you several tries to get it all.
When you tear the foreskin away, the head will be red in color, where the separation occurred, for a while. Put some Vaseline under your foreskin to prevent it from re-adhering to the head.
You may also try "ballooning" your foreskin by pinching the tip shut when you pee and causing the foreskin to fill with pee. That will lift the foreskin away from the head and tear loose the fusion.
If you can’t get it to separate by pulling on it, a urologist can help you. It is called “lysing”. Don’t let anyone sell you a circumcision. It is not necessary and extremely harmful.