Have been peeing blood for three weeks, pain in lower stomach and left side. dr. did urine test, showed whitecells, been on two strong antibiotics for two weeks. shouldn't it be better by now?

Yes . . .: Yes, assuming correct antibiotics. Most of time, we just guess at need for antibiotic w/o identifying specific organism causing infection. So if you're still feeling poorly after 2 different antibiotics, it's time to stop guessing and obtain culture & sensitivity to identify bacterial. Go back to Family Doc for further testing. May need to get xray or CT. May need to see Urologist for endoscopy.

Possibly: A urinary tract infection (UTI) can cause pain and blood in the urine (hematuria). And if it is a simple infection, then a short course of antibiotics usually cures it. If they don't, then it is by definition not a simple UTI. Other potential causes include a kidney stone, diverticulitis and cancer, among other things. Your MD has a plan A, B and C for this Keep your next appointment.