I'm 14 years old and I, as you probably guessed, frequently masturbate. But I can only do so by rubbing the foreskin over the head as it is too painful to pull my foreskin all the way back, also there is a small strip of skin connecting my foreskin to the head of my penis and I am scared this is going to result in a lot of pain during sex. Any advice is extremely welcome.
It's not uncommon for it to be difficult or painful to pull your foreskin back at 14. Usually by about 16 it will stretch enough so that you can move it easily.
The strip of skin, is it on the underside of the glans? If so it is likely the frenulum and is normal. It should stretch as well.
Give yourself some time.