I have been having severe back pain. I am 34 weeks and my doctor told me if the only way I can find relief is the heating pad and a hot bath then that is what I need to do, I alternate and it has been helping. She said it will not harm the baby. You know your body, just make sure your body temp. does not get too high.
I'm 27 wks and my back had been Killing me for months now! Tylenol and the heating pad are my best friends
Don't use a heating pad, for the same reasons you can't get in a hot tub. It's too much heat for the baby.
Maybe take a warm bath. How far along are you?