Ugh, reading about your symptoms reminds me of some stomach stuff I had around two years ago, when I was probably at my lowest cals. I'd always figured I'd gotten some sort of bug, but since it happened more than once it was probably my body rejecting some sort of nutrient I'd denied it too long.
I also remember reading in MRM about undereating leading to pain in the joints, which explained the shooting pain I had in my right arm for about a month running. Had an EKG and an ultrasound done; neither one revealed any problems. My GP had no idea what could be happening. Eventually the pain went away--I assume when I upped my calories a small bit; can't remember now--but man, the things we do to ourselves!
Sorry your body isn't happy with you right now, but things will get better in the long run. Your rising temp and lowering HR are already good signs.
