Really sore pain! Answers needed....?

I kept getting really sharp pain on the left lower side of my stomach, I thought it was maybe just wind (gas). So I left it for around a week, but pains were getting worse even waking me in the night. So I went to my GP and she was feeling my stomach, even pressing on the left side by the bladder was really tender. So my doctor done tested my urine and found Nitrites, Protein and Leucocytes and said it was suspiciuos for infection and gave me a three day course of anti-biotics. They didint help so went back to the doctor ten days after with the pain getting stronger. So she examined me and my stomach was still very tender and tested my urine again to find the same as above but also with blood, and the nurse asked me was I on my period, which I wasnt,on the pill at the moment. She sent the sample to the lab to be tested and my results came back with No Infection. The pains are still here mostly all the time now, getting worse! Any Ideas on what could be wrong? Any experiences? Thanks to all in advance.