I'm really worrying about my dog?

First of all, you're full of crap. AKC doesn't even register pitbulls- they register AmStaffs- not American Bullies (which aren' teven APBTs that UKC registers). And no one takes their dog to the vet every month. So, just fess up that you just have a regular dog and you're a regular owner. Usually frequent urination is a symptom of an enlarged prostate. The meds are likely doing their job, but maybe a little too well. Talk to your vet about lowering the dosage.