I feel if you are that unsure I wouldn't get the injection. Can you with stand the back pain until after you have the baby? If so then wait. I also have back pain and post on the back problems site. Being pregnant also adds to back pain. The injection at this point may not help too much any way. I tend to agree with the doctor to some point about it being ok to get the injection. You never know what can happen with it though. My last injection caused some spinal fluid to leak and I had to go in for a blood patch. This is done under an x-ray machine. That is some thing to consider. You don't want to be exposed to that if you don't have to. If you are that unsure hold off on having it done.

I'm sorry if I was no help.