Back & Thigh Pain

On April 8th, I went to the doctor with low back pain & burning sensations in my left thigh.  The doctor diagnosed me with a lumbar sprain.  He did check my reflexes and my leg strength (hitting my knees with the the little hammer & asking me to push up with my thighs while he pushed down on them.  He seemed to find no issue with reflex or strength.  So he put me on 10mg of Flexeril 3xs a day for 5 days, and 500mg of Naproxen twice a day for 10 days.  

I had started to have some improvement after the prescripts ran out; with little back pain and finally able to sleep through the night.  But, I went back on April 30th, with a return of the previous pain and pain radiating into both my thighs (sometimes a shooting pain, sometimes a dull ache).  I sleep on my back (it's the least painful) and sometimes I awaken to shooting pain down my left thigh.  Plus I am now getting symptoms affecting my right thigh; although I guess that could come from trying to keep pressure off my left leg.  I did have some housework/yardwork to do, but I tried not to strain anything.  Aside from the back and thigh stuff mentioned above, I'm also getting numbness in the back of my right thigh when sitting too much, especially driving.  

I have been trying to take it easy, but the driving can't be helped since I have to drive my mother (who has just gone back after having a mild stroke in Feb.) back-and-forth to work for the time being.  I have tried a lumbar support pillow (at home and driving), also plenty of heat, a softer mattress and sports creams.  Still, it feels like I have run a marathon.  

Anyways upon returning to the doctor this past week, he prescribed another round of meds., same dosages, etc., and is sending me to physical therapy for up to 12 treatments.  After that, I am to return to see him; if my back is not better, he is recommending an MRI to see if it could be a herniated disk.  Unfortunately I don't have insurance at this point, so an MRI is probably out of the question.  Also, I am only 33 y.o. (female) and never had back issues before.  Last summer I was landscaping with no problem.  This is all new to me, and I don't have the funds to be looking into the wrong causes.  

I would really appreciate if someone could tell me if a Lumbar Sprain seems right for my symptoms; and how long something like that should take to heal up.  Again my symptoms are: Lower Back Pain, Dull Aches/Sometimes shooting pain in the fronts of my thighs, and numbness in the back of my right thigh while driving.  

Please help.  

[Catalina92]

Perhaps it was a bit much to say I feel like I've run a marathon.  However, I'm just not doing extensive amounts of physical activity that would cause my thighs (sometimes knees) to be so sore.