Back rubs always helped me, but obviously people can't walk around rubbing your back 24/7, so I would try the therma care portable heat patches if you are not in the position to use a heating pad, but check with your doctor first. They can get pretty hot and I was always told to use low heat. So, check with your doctor or midwife just to be sure it's okay.
I havnt found a sure thing to help but a heating pad helps some