Important Question! Please read & Answer!

Okay ladies! I need some help! I had my first transvaginal ultrasound on Jan 21, also sex the 22nd. The next day, I experienced some brown discharge, my doctor said it was perfectly normal. I ended up going to the doctor again for the continued discharge last week and they did a pelvic exam, my is is closed (which it is supposed to be) and the doctor said everything looked great that he thinks I'm low risk. WELL, I did have a UTI, so he gave me a prescription to take 3 times a day for 3 days. The nurse said if it bothered my stomach to just take what I could. Well I did and I wasted 3 of them due to M/S. I called my doctor and she said I may still have the infection... But I don't have any of the symptoms. I have some of the same pills left over from another UTI that I could take to insure that it is gone, but I don't want to take them if I do not still have the infection. My mom think I should just wait till my next appointment in 2 weeks , until then keep drinking water and cranberry juice. I had sex two days ago, and now I am having the brown discharge again. SOMEONE PLEASE GIVE ME PEACE OF MIND AND TELL ME WHAT TO DO!!