Upper back pain!!

I am having some pretty bad upper back pain right now. I am 37wks and it hurts so bad. I have been put on bed rest and so I've just been laying in bed all day but I can't seem to get comfy. I have been trying to change up my positions and stretch my back out but it doesn't seem to help. It helps maybe for a few seconds and then it's back. Any one with similar experiences know what this is about or how to relieve it?