How long has it looked that way? If it's just once or twice it may just be an upset stomach. Undigested worms can happen if they don't chew completely and eat a lot at once or in a hurry. If it keeps up like that for a few weeks then you may want to have a sample checked by a vet. As far as temps go, 37 is OK but you may want to try bumping it up a few degrees. Maybe in the 38-41 range as long as you have plenty of space away from the basking area that is cooler (24-27 ish).