BAM, I agree with Phyllis. The only way to find out what is going on is to have a vet examine and run diagnostic tests.
I couldn't get a urine sample from my boxer and my vet gave him amoxicillin based on symptoms and his past history of no urinary tract problems, but a few days later we did get a urine culture, x-rays to check for crystals, and strips to test for blood in the urine.
He didn't have crystals, but there was blood in his urine (strips didn't pick up bacteria but that is not uncommon) and the urnine culture came back 4 days later with high concentrations of e-coli (infection). It took 3 rounds of antibiotics with urinary tract support supplements to clear up the infection.