How To Treat Pain,stiffness And Numbness In Lower Back?

Okay im a college football player and I have a back problem that ive had for the last 5 years. MRI s and x-rays say that my back is structurally fine and that it appears to be nothing wrong, but I experience everyday pain, stiffness and numbness in the lower part of back till the point where I cant move. I cant perform properly, sit down lie down or anything for a long period of time. ive strengthen my core and everything else but nothing seems to be helping.