Blood In Stools, Very Sudden Since This Morning, Very Bad

Blood in stools, very sudden since this morning, very bad chills when outside, in last hour when getting home on subway/bus, trembling chills, even though I have 4 layers on and heavy coat, normally not a problem; painful back (ache) but I did a lot of shoveling and snow blowing yesterday, body aches, but hard to relax; somewhat nauseous but feel a bit better after tea and toast. Fatigue. Hot right now but my wife is "blasting the heat."

I work at one of the Boston hospit.als and my primary is good.

Thanks