lacie, I'm not a vet, I'm just talking from past experience. If while he is basking, he keeps his mouth open just a crack, sometimes, it's just for a few minutes at a time. This and the basking, lethargy, are typically symptoms of a respitory infection. If you can afford it, a vet visit will get him the antibiotics he needs to fight off the infection. I hope I'm wrong, but wish you luck. Checker.