Please be aware that a thermostat is NOT optional. Without one, your UTH can easily reach over 100 degrees and burn your snake! As mentioned, please unplug it until you have it connected to a thermostat. So that may be one of the several reasons that your snake is stressed.
https://www.amazon.com/gp/aw/d/B000N...art+thermostat
Here's a link to an affordable thermostat. I'm confident that once you fix your husbandry issues your snake will eat!