Welcome at HCM.
I have read your question completely.
It looks from your details that you are having pain at your back which is radiating to lower limb.
This pain is known as sciatica
.This is a symptom.
This is caused by following reason-
-Compression of nerve
in back due to enlarged disc.
-Compression of nerve in back due to spondylosis
-Compression of nerve due to muscle in hip known as piriformis.
To rule out all these you should do following-
-Consult to a orthopedic surgeon.
-Have complete investigation including MRI
-Take a nerve analgesic
Hope this all will help you.
With best wishes.