I had what I call a "boa constrictor" for about 6 months. Mine started right at the bottom of my rib cage, and would squeeze down to my thighs for about 30 seconds at a time. It would wake me up in the middle of the night barely able to breathe as it would grip me so tight. It actually hurt my lower spine. Day time it felt more tingly and didn't affect my breathing. Not sure if this is the same as what you are experiencing? I was sent to an MS doctor and had an MRI ran before he quit and moved out of state, but after he moved no follow up was done. My boa constrictor thankfully seems to have moved out of my house.