Even though you have repticarpet, they can still burrow to get to the warmth. I second everyone elses opinion to get a thermostat ASAP and get a temp gun or a thermometer with a probe to put on the heat mat.
I also agree with what Mark said. if it feels warm to you, it's too hot for your BP.
Like everyone else, I hope he's pinking up before another shed however, I feel like it might be the start of a burn. Unplug the heat mat until you can get a thermostat and keep an eye on the pink belly.