I suffered frm prostate ecoli infection n uti frm aug 2015. semen culture report is -ve so antibiotic stopped frm 7 jan 16. my scrotum remain tight y ?

Sounds OK, but...: This doesn't sound like you have any serious ongoing problem. It isn't unusual for genital area discomfort ("tight" scrotum, etc) to continue a long time after this sort of complex infection. You're obviously under a doctor's care; ask him or her. If things remain uncertain and you have not seen a urologist or infectious diseases specialist, that would make sense as the next step.