A weird side effect of insomnia?

This may sound odd, but I've experienced this for about 15ish years. I'm already a hot bodied person, especially now that I'm adult & overweight. (I wasn't always) But at night it definitely gets worse. I usually spend between 30 minutes to several hours CONSTANTLY switching from laying on my right side, to my left side, to my stomach, to my back, and repeat.

What makes me do that is embarrassingly.. my butt. It feels like it's on fire. I'm 20 years old and since I was about 4 or 5 I have to go to sleep laying on an ice pack. It kind of numbs all the heat so I'm focused on a different feeling- the coldness, and it usually helps put me to sleep. When I wake up in the morning I'm not hot though. I'm usually very comfy, sometimes even a bit chilly. It makes me dread going to sleep, dealing with that every night. I plan on seeing a doctor soon but has anyone experienced that? Or at least one specific body part overheating at night?