Bladder UTI Lower Left Abdomen Pain?

[babyeedoll]

I've tested negative several times for UT infections, but continue now for months to have acute lower left pain in my colon & bladder. I have a hard time urinating, I urinate frequently & theres a pain in the lower bladder /colon area. I'm 18weeks prego, but had been suffering with long bouts of this type of pain starting over a year ago. I have existing gastro issues, which don't have a real solution, so I've been hesitant to see a urologist, thinking I'd go through the same thing as I did w/ the gastro doctor (i.e. many costly / time consuming tests). I stopped at the colonoscopy, b/c that would only realisticly rule out cancer. I'm a 30 yr old generally healthy woman. I've been taking cranberry supplements & am on a low dose prescription antibiotic for UTIs, which as the doctor said, is not meant to prevent UTIs, only reduce their severity. What could this pain be?