I Had My Cycle On December 2nd It Lasted For

I had my cycle on December 2nd it lasted for 8 days I had unprotected sex with my partner on the 12th now I'm having some cramping and lower back pain with a little nausea and headaches I'm feeling tired went to my doctor they took a pregnancy test it was negative and did urine samples for bladder infectionan STD came back negative but I'm still having a little discharge with little white specks in it what could this mean and why do I have to pay to ask a question