just try your son to sex may be it can be loose. I am also same before but I start sex with some older womens then its solved
circumcision is fine for sex. Some women are turned off by uncircumcised penis. I doubt a woman would ever say "ewww you are circumcised"
How old is your son? If he is under 15, it is actually too early to be sure he has a problem with his foreskin.
you may try to massage in a particular manner with coconut oil.. Inserting finger between foreskin and glans. Rotating finger is one way to massage. Another is pulling the skin back making the hole wider.(not urethra's hole). people have different opinions about the circumcision . It is true that foreskin has lot of nerve endings which adds pleasure in sex. What is his age?. Doctor's opinion will be important.