Usually, the hot feeling comes from acid burning you.  When my younger son was a baby, his stool was so acidic that the instant it came out of his body, it would burn his skin (I mean a real burn) because it was too acidic.  I had to always apply a thick layer of balmex cream all over him in order to protect him from it, but it usually wasn't enough.  We later found out that he is lactose intolerant, and his body just wasn't digesting dairy products well.  When we modified his diet eliminating lactose (dairy products), and later began taking lactaid, the hot sensation and burning stopped.  I'm not saying you're lactose intolerant, but you might want to ask your doctor if he thinks your burning sensation comes from the stool being too acidic, and if so, what are you not digesting well?

About internal hemorrhoids, they should not cause a hot feeling or burning sensation.  External hemorrhoids could cause itching and pain, but I’ve never heard of burning sensation.  Burning comes from an acidic stool.

The fact that you are very constipated could be the culprit of your problem.  You need to get regular, and then check further for food allergies to see what could be causing the hot feeling.  Ask your doctor.

Good luck,

mpdela