Lower Back Curves Sideways, And Will Not Straighten. Help!

I should start by explaining some of my back history. I have herniated disc L4/L5. I have had this problem for about 6yrs and can almost guarantee it will lay me out for a week or so at least 2x a year. Except for those aganising weeks I pretty much am pain free.

Four month ago I became pregnant. Soon after that my back went out on me and has yet to be "normal" again. The problem that Im having is that my back will not straighted out when I stand. From the bottom of my rib cage down it either curves completely to the left or right side. It actually switchs back and forth. Causing one leg to be a lot shorter then the other.

Its getting worse every day and Im getting more pain down my legs every day. Im hardly able to function anymore.

My PCP is thinking that my back is spasming and the pregnancy hormones are causing havoc. But she doesnt know for a fact because they are unable to do an MRI b/c of the pregnancy. They also had me try Flexeril (muscle relaxer) Prednosone (anti-inflammatory) and neither has made any difference. ( Yes, Ive made apsolute sure these medications are safe for the baby) The good news is that the baby seems to be doing great and is not being effected at all this.

My question is- Does any have any experience with this type of back problem? Any help would be so very appreciated. Thank you for your time.