Recently treated for uti. last urine/culture showed clear. still having symp of pain into low ab and back after peeing. cause?

Many Possibilities: Persistent symptoms should prompt a repeat evaluation with another culture, exam and perhaps an ultrasound. This could be due to a kidney stone, ovarian cyst or resistant infection.

Needs attention: Any discomfort during or after voiding needs the attention of your gynecologist. There are several causes. You will need a pelvic exam and some tests - at a minimum cultures for gc and chlamydia , pregnancy test , pelvic ultrasound etc.