You know it's an RI when you take him/her to a vet and the vet says that what it is. There is nothing I can tell ya over the internet to diagnose an illness. He really ought to be seen by a Dr. to be sure it's not serious. It SOUNDS like he has an infection and he needs more belly heat, though nothing higher than 95-96 at the hot spot. If you have a lamp, it is ok to bump up temps with it to dry things out for a few days, but you really don't want to lower humidity with it all the time, just when he's sick.
Lastly, take him to a vet! Pets are expensive and if you are going to have them, you really need to be able to take them in in an emergency! If he is sick, putting it off is risking his life...