Lower abdomen pressure


For the last three weeks every time I have to pee or right after I pee I get a lot of lower pressure. Like to the point of where it hurts to sit or stand. I brought this up to my doctor last Thursday and they did a urine culture. It came back negative. The nurse on the phone that gave me my results just said to drink more fluids to see if it will help. I've tried.. nothing helps. Has this happened to anyone before? Is it just normal since I'm 25 weeks?