Postcoital bleeding most times wen dry for over a yr, no std, pap smear and pelvic exam are normal, what could be the cause, becoming a bother :/?

Lubricant. If you have had a negative pelvic exam this may simply be due to trauma to the mucosal wall of the vagina because of lack of lubrication. There are numerous OTC products available. Check Amazon, CVS, etc. Also, Cosmopolitan magazine has had articles about this. Good luck and I hope this helps.