Pink belly

[Bogertophis]

... I only have the UTH on 12 hours of the day and the hottest it’s ever gotten was 100 degrees. It only reached that temp when I left it in all day and night...I got him a month ago from pet smart. He has not went through a shed yet. Right now the tank humidity is between 55-60%. Is it more likely he is about to go through a shed than it being a burn?

If your snake was in the cage when the UTH got to 100*, yes, it's possibly a burn. How is your UTH being regulated? You NEED a thermostat to control it 24 hours a day.
You also said "when I left it IN..."? I hope you realize that "UTH" means Under Tank Heat...meaning it does NOT belong IN the cage? Just checking...it's dangerous to run
UTH inside the cage, because your snake will likely spill some water (or just the humidity) & may die from electric shock...UTH is not designed for safe use inside a cage.
Note, thermostats are not the same thing as thermometers. Thermostats control the power, thermometers only measure whatever it is.

If you are turning the UTH off at night, how cool is his cage getting overnight? I'm guessing it's too chilly for him, but it depends on your ambient room temperatures too.
There are snakes that can tolerate a significant temperature drop at night (without getting sick) but BPs are not one of them. He needs temperatures between 78-80* on
the cool side and about (slightly below) 90* on the warm side...and he needs this 24 hours a day, 7 days a week...or he'll be getting sick.

It's still possible that he's going into a shed (hence the pinkish belly) but I'm not there, seeing your snake...so no guarantees. I sure do HOPE it's not a burn.