I Went To The Dr. Because I Was Having Sharp

I went to the dr. because I was having sharp pain when urinating and thought I had a bladder infection. She prescribed antibiotics (which were quite expensive) and I started taking them. She called back and said that my urine lab came back and I did not have a bladder infection. I asked what was wrong then and she did not know but told me to drink a lot of water and if it did not get better to go back in. Any suggestions?