Two Nights Ago I Developed Severe Pain In My Lower

two nights ago I developed severe pain in my lower left hip/ outer buttock area ( felt like someone had hammered a bolt into my side and was putting pressure on it). Spent the following day in emergency; was given morphine for pain and a urine sample was taken, which nursing staff said 'had bugs in it'. However I had no fever, and no burning when urinating, though my bladder area felt tight. I was urinating infrequently despite water all night and day. Doctor sent me home with script for painkillers, as he suspected back injury. However I had twenty four hours almost pain free. Now I am in agony again. Nothing helps, except for walking sometimes. I have also had very loose bowels since this started. I am thin, and fit. What should I do now?