Symptoms of Crohn's Disease like bloody diarrhea can indeed be caused by mercury poisoning. Here's one list of symptoms that mentions it.

http://curezone.com/dental/mercury_symptoms.asp

I had a terrible bout about a year and a half ago after never having had that happen before. It was very scary, painful, and indeed felt life-threatening. I had zero energy and turned pale as a ghost.

Symptoms of Crohn's can also be caused by a Lyme infection, and I have that too. Though I didn't know I had either at the time. I took Flagyl which is one antibiotic used for Crohn's, which ironically is also one given for late stage Lyme. So it helped in my case.

Yes, the coldness probably is caused by low thyroid. Mercury poisoned and lymies both are low on iodine, so taking iodine like Lugol's liquid will help a lot. It also helps your body fight infection. There's a place called jcrow.com where you can order it cheap.

I've only had two more bouts of bloody diarrhea since starting to treat both lyme and mercury poisoning, and both were while herxing from taking too much stuff for lyme. But not nearly as bad as the first one. I don't know exactly which one caused my Crohn's symptoms but it was probably a combination of both.