I'd suggest you go see a urologist. They can separate your foreskin from the glans - safely, and without leaving a scar. By now, it SHOULD have done so on its own. Don't just pull it, it can scar.
Yes, you can have sex. Use a condom and keep your foreskin up.
Just be aware, your foreskin may roll back and tear the adhesions causing some bleeding. It may even get stuck behind the glans.
You need to stretch your foreskin too Sam.
Get to the doctor ASAP. You have a long life ahead of you and don't want any difficulties in the sex department.
You are blessed with an erogenous, highly-innervated foreskin. Many unforeskinned guys would envy your foreskin. You display great wisdom in wanting to avoid circumcision. Do not be worried. You are normal for your age.
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.
You can still have sex in the way that you mentioned.