My gerbil fell ill 10 days ago, he was cold and inactive, but later eating. We moved them next to a radiator, he continued to improve, but a few days ago we noticed that he had lost a lot of weight, he has always been skinny, but his spine was very pronounced, and he would not eat. His eyes were half closed. The next day he ate 4 mealworms, some bread and some strawberry, but would not drink. Today he ate some bread, strawberry and a Mealworm. He didn't take anything dry like seeds. Seems to have more energy, he drank. Eyes are still dull and half closed. Any ideas of what is wrong with him.