A cold animal will be lethargic, just lay there, no interest in food, etc. But since yours has diarrhea as well, he has something else going on. He may have picked up some intestinal bug from someone in the family or if you feed him greens from the yard, they may have been contaminated with something. The only way to know what's causing this is a trip to the vet. They can do a fecal to check for problems and prescribe the proper medicine for what ails him. He may need some supportive care for a day or two - IV or subQ fluids and heat.
My guinea pig loves her house. She only comes out to eat. Maybe you should get her a house. Make sure you don't feed her too much citrus/or veggies. Keep her on pellets only for now.
thank you but before i had a chance to take him to the vet he passed away, from his waist down he could move anymore and breathing was hurting him and then it was to late...
I'm so sorry your piglet died. I've had guinea pigs before and they're so sweet. If you plan on getting another, make sure everything is well sanitized with some bleach and water. Don't want that heart break again.