Obviously can't diagnose but based on personal experience, it sounds like ms hug to me - during a relapse last year, my rt arm went numb, then my entire body from chest down (plus other symptoms). I remember the chest thing being so unpleasant that even leaning back against pillows was horrible - anything touching chest, abdomen, back made me so uncomfortable and the pain was bad from spasms. This eventually disappeared, and some symptoms remain. I have since had it return during an exacerbation - regular pain killers don't help - maybe ask for something for neuropathic pain from your doctor and try that - even for your other ms related pain - either neurontin or similar for neuropathic pain or baclofen or similar for muscle spasms.
Hope you keeping well.