More often than not, when I walk more than about a block, my upper back tighten, my left shoulder locks up and I get really hot. I don't sweat, but it feels like someone has wrapped me in a blanket. I do have back problems and have been diagnosed with Fibromyalgia, but it doesn't explain why my body reacts like that. It takes awhile for my temperature to return to normal, but the back can stay tight for hours. I had all types of caradic test ran and no one can tell me anythikng. Can someone please help me? I'm scared I'm going to collaspe when I walk anywhere.