Sounds like your heating pad is NOT monitored by a thermostat and has gotten too hot and/or is failing. Possible infection or cyst growth. I would take it to a VET and see what needs to be done. Maybe draining or antibiotics needed. You NEED a thermostat to control your heat pad. And if you're using two bulbs with one fixture, just use the night bulb. The snake can tell night and day with just ambient room light. If you're switching your bulbs out daily their life will be significantly reduced. Get a second fixture or just use the night time bulb 24/7.