persistant UTI

Has anyone ever experienced this or can shed any light?
I have suffered with recurrent UTI's for years but a few months ago had a particularly severe one which I took 4 different antibiotics some not finishing the course because I felt they weren't working (stupid I know, probably the reason Im in this mess I know). I dont think it ever really went. But my urinary symptoms completley died down after a course of trimethaprim. After about a month I became severely brain fogged and tired and weak and couldn't do anything. I thought I had ME. I had strong smelling urine and occasional twinges when weeing but no normal UTI symptoms. Then after a while it transpired I had a UTI. The sensitivity test said it was sensitive to amox so the doc put me on 250mg 7 day course. The symptoms improved but didn't go. I then had a 5 day course of 500mg amox and the symptoms seemed to lift. I was so happy to feel clear again. 2 weeks later the symptoms have slowly crept back and I am now brain fogged again and have strange urinary symptoms-slight stingy twinge on weeing and lower abdominal pain/gripes but without the fatigue. I got drunk with my friends a few days ago and that seemed to make it a lot worse. I am a 5th year dental student approaching my finals and I cant think straight. I just failed a practical exam and my tutor said I just didn't seem with it. She was right I never feel with it at the moment. It is making me so sad. I feel like I have a superinfection. Oh and now my urine tests keep coming back negative apart from slight white blood cells and the docs keep telling me I am making the symptoms up.