Excruciating back pain ideas?

B

Currently 24wk3d w my third, first time w anterior placenta though. Back pain has become unbearable the last 2 wks, to the point that I dread car rides. Sitting is the worst and now my right leg/foot goes numb driving. Went to doc, assigned me PT, a week off work, & Flexeril 3x a day. Only taking the med 1x a night since I have to function. Its not working though & it appears neither does heat/ice/or any topical creme I can find. I had to use 40hrs for missing work this wk & am now stressing how to make it until Jan. (Req by employer to use a month personal leave before lil is born).

Anyone else have suggestions? Never had this type of back pain w my boys, and any that did occur was at the very very end. Weighed with my youngest @ 180# just before birth. My normal weight is 130#, I'm at 157-159# right now.