Suffering From Horrible Upper Back Pain. What Could Be Cause Of It ?

Every once in a while I will be woken up in the middle of the night, with horrible back pain. It starts in my upper back, then goes to my chest and them stomach ; It never happens in my lower back. It feels like I m being crushed to death and I can t breathe. This happened to me before while I was pregnant, so at the time the time I thought it had to do with contractions (went to ER while pregnant, turns out I was dehydrated) but now that it s happened about 5 times post pregnancy I am beginning to think it has to do with something else. I have no idea what is going on, I ve debated on whether to head to the hospital when they happen but unsure if I should. Has this happened to anyone else ? I was thinking may be I could be dehydrated ? I ve tried drinking tons of water and gatorade but nothing is helping! It hurts to even sit or lay down. I really would like to know what s going on! Please help!