Why My Penis Foreskin Does Not Retract?

sir i m a man living in dehradun india ,40 yrs old heiht 5feet 9 inches weight 59 kgs. my foreskin is very tight and does not go back during intercourse. therefore i i cannot enjoy sex fully. i already had undergone a minor surgery at cmc dehradun about 10 years ago as the foreskin was attached to the penis .this has loosened the skin but when in erect position it becomes tight. please help me.