Hi,
You are having pain in the Lower back (throbbing in nature comes and goes) more on the right side, which does not allow you to sit, lye or stand. You are not able to sit erect and you have to sit like a old man bending your body. Even while in bed also the pain so much, that it disturbs your sleep. The pain does not allow you to sleep on your front as its too painful, the best is on your back with your knees up. Warm bath does not relieve you. You had once UTI which was treated and the recent investigations show NO UTI.
Treatment:
1) A routine USG - to rule out any other cause other than spines. (kidney,
ureter, bladder and
appendix etc.,)
2) If USG is normal, straight away do MRI Lumbar spines with Lumbo Sacral joint. This will reveal any spinal pathology.
3) Routine
blood test for WBC, DC, ESR, HB, MX, HIV, sugar, Urea and
Creatinine, along with ECG, BP and
Lipid profile if indicated.
I think with this, the diagnosis will be very obvious. Treat the cause if any, You will be alright.
Best wishes