I have a bladder condition called Interstitial Cystitis which was just diagnosed by a urologist about a year and half ago - just a few months prior to my last conception. The way I understand it, my body is essentially "allergic" to my bladder, thus it is usually a bit swollen and easily irritated, and an irritated bladder means bladder infections, UTI's and kidney infections. (I passed kidney stones at 16 wks with my first baby. You really don't want to do that.)
First of all, DONT DRINK CRANBERRY JUICE! It's an old wives tale and compounds UTI's. It's a very acidic juice and the more acidic the product, the more it will irritate your bladder and urethra and compound your problems. Other dietary restrictions with a UTI include but are not limited to, citrus (fruit and juices), ANY caffeine (coffee, tea, pop, chocolate, etc), nuts (except almonds)....some restrictions are more intuitive than others....
Because of the IC and my prevalence toward UTIs, bladder infections, and kidney infections, I was put on Nitrofur - an antibiotic strictly for the UT region - through the length of my last pregnancy, as well as continuing the Uresed - antimicrobacterial with an added numbing agent to deal with the pain - I take regularly.
I would first and foremost, talk to your OB. Secondly, see if you can't get a referral for a urologist. (Btw, most urologists I've met are nasty-tempered men who think women can't wipe right and that's where all their problems come from. Plus, I've decided they probably only seek a specialization in urology bc they can't hack it elsewhere but have to use their medical degree somehow - yes, the urologists I've encountered are that bitter and obviously hate what they do. That said, if you can get a consultation, they'll want to run all sorts of not-so-fun, but necessary tests.) Third, don't have sex until you get this thing cleared up. Sex will make it worse too. Also, glad that you're drinking water, but that's ALL I would drink. Maybe some milk. But drink at least 100 oz of water/day. During my pregnancy I had to drink 160 oz/day...
Lemme know how it goes and if you get it cleared up....what works.