Here's some things to try
- Clutter up the cage. I bet it's a bit big. Use crumpled newspaper, more hides, plants, etc. Cover at least 75% of the floor space
- I don't know if you're feeding live or frozen mice, but try live! Sometimes it just takes a little bit of time
- if your snake is 3 ft, it's probably an adult and is off feed do to the breeding season.
- Buy a scale and keep track of the weight. If it isn't losing weight, I wouldn't worry too much about the snake not eating.
- get some identicle hides for the hot/cool side - they will favor hides over thermoregulating
- your hot side might be a tad hot. Bump it down to about 90-92...but to do that you will need a thermostat or table top lamp dimmer ($10 at Home Depot).
- GET THAT THERMOSTAT FAST! You really, really need to get one of those. Buy a cheap one (Hydrofarm) off amazon. It's like $30.
Good luck!