Lower back pain. How to proceed further?

PROBLEM : im facing a pain in lower back a tightened feel , when it released a huge gas is produced and its free if not then pain radiated to thighs , shoulders and even causes me severe headache and if tightened feel in low back continues means there will be difficulty in going bathroom and urine ,  I dont know what's happening in my body , in my mri reports showing everything is clear but still  standing , running causes tightness in thigh and causes me headache , if i keep on tightening my thighs it produces me massive headache and severe pain in whole spinal cord , can anyone suggest me whats my problem from this Mri and how can i proceed further , because i have consulted many doctors but everything in vain , kindly suggest me how to proceed further