Lower Back Issues

I'll try to keep it brief.  Near the end of my pregnancy I was sitting in the shower and suddenly realized my butt was numb.  Next morning I had severe shooting pains down my right leg from the butt.  My OB said it was sciatica and gave me pain meds.  I was miserable for months, with the highest pain meds (narcotics, I forget the name at the moment.  Tried vicodin and then there was another one after that that was supposedly "stronger" -- neither really worked) doing practically nothing.

After I had my baby I still had trouble with pains, but mostly with the feeling that I was sitting on something.  It's really hard to explain, but right around my tailbone area / where my cheeks come together it feels like I'm sitting on something hard.  It used to feel like I was sitting on watery blisters (without the pain part).  It's a feeling that drives me absolutely crazy.  I can't sit comfortably.  When I stand or lay on my side at night the sensation goes away some but it still feels weird there.  I also have a feeling of numbness in the groin / perineum area.  Also, the backs of my calves are sore like sore muscles if I put any pressure on them, and the instep of my foot hurts the same way also if I step on something hard / off.  It's like my muscles are constantly tight; not spasming, just never relaxing!

I had a Lumbar MRI, it came back with a bulge at L4-L5 and a moderate herniation at L5-S1, and I believe they said it was causing my spinal canal to be a bit narrowed.  I went to an orthopedics place and they sent me to physical therapy since I wanted to avoid drugs while I'm nursing.  The PT helped some; apparently my piriformis muscle was causing some issues and the feeling of sitting on blisters has gone away, but now I feel the sitting on something hard feeling even more so.   We did a pelvic MRI, but that didn't come back with anything other than a slightly tilted uterus (of no consequence to this), a dilated blood vessel (told again of no concern to this), and again the herniation at L5-S1.  No lesions, no bone spurs, etc that could be causing this.  I've looked at a dermatone map, and the feelings are in the areas supposedly supplied by S3-S5 (for the butt and groin).

My doc seems to think that there is nothing on the MRIs to indicate what is causing this issue.  When I press for more I feel like I'm getting the brush off because of the insurance I have.  I've been scheduled for some epidurals, but as the doc said, those are usually for pain, not for numbness / etc.  SOMETHING is very wrong and it's been 9 months like this.  It's hard to concentrate, I have to constantly shift positions I'm sitting in.  I really don't think the steroid shots are going to do anything but as near as I can tell these are my only options besides surgery.  

What in the world could be causing this?  I'm only 28; I am searching for work and really would like to have this resolved so that my mind isn't constantly on this and I can actually sit at a job for 8+ hours when I need to.  I do occasionally have pain; it is in the back of my thighs and comes on suddenly, radiating out like the branches of a tree making me think it's a nerve flare up when it happens.  But it's really this 24-7 never ending feeling like I'm sitting on something / someone is trying to shove something up my backside that is driving me crazy.