Cramping after peeing

Currently 33 weeks but I've been experiencing sharp cramps after I pee since I was 31 weeks. I've brought it up to my OB and had some urine tests ran, but they all came back negative. She doesn't seem too concerned but sometimes the pain is so unbearable! I know the baby is head down and I can feel it in my pelvis but man, I wish I could skip peeing all together now. Anyone else experience this? Is it just the baby pressing on something?