Muscle Spasms at 36 + 4

So I've gone to the ER two times in one week due to extreme back pain. 1. The first time it felt like I was being squeezed around my body, this was felt around my ribs and beneath my breasts. The squeezing went all the way around my body and was consistent. The pain was too much and I ended up throwing up and the pain went away after three hours or so. Apparently I was having some contractions and the nurses chalked it up to dehydration. (to me it's obvious because I had just puked so I didn't believe that was the real reason.) 2. Around 4am (only 3 hours after I just got back from the ER) the same pains and nausea came upon me. I did as the nurses recommended for dehydration, drank water, took Tylenol, and took a hot shower. Well, on my second bottle of water I ended up throwing up all of the water and the pain went away by itself after about 2 hours just on it's own. 3. Two pain-free days went by and around 11pm that night the back pain slowly returned. Again, I did as I was told and still nothing. My back was in so much pain my body wouldn't allow me to throw up (as those my were the muscles needed to perform the act) After two hot showers and some labor-like breathing I was still in debilitating pain. The pain had never lasted this long so around 4am we went back to the ER and I had no signs of dehydration or contractions, just pain. I was given IV fluids and had my blood drawn, finally around 7:30am I was given a small dose of morphine, because now I was pushing 8 hours of extreme upper back pain. My doctor said it must be muscle spasms due to increased hormones at this stage. Has anyone else experienced this?? I'm scared any small pain in my back will turn into a full-on spasm! HELP!