If you've been circumcised you don't have a foreskin, or if you do the circumcision was done incorrectly.
Stretching exercises just might solve your problem (search the internet for Manual Foreskin Stretching instructions), with or without applying Betamethasone to widen the opening. But caution: don't tug too hard at any time, and certainly not with B. , as it works by thinning the skin. If your foreskin when retracted behind the glans is not restrictively,, uncomfortably tight, then there's no real problem with either masturbation or sex. However, if in intercourse the foreskin opening slides back onto the shaft and causes a restrictive bulge, that's a serous problem that needs your doctor's attention.