Wannabe Mother Hen
This is more adorable than it is embarrassing. In kindergarten, your teacher probably brought an egg to class, and you and your classmates waited several weeks for it to hatch. After trying the experiment in class, the OP probably felt inspired to try it at home.
The problem is they used a grocery store egg instead of one from a barn. Grocery store eggs have like a 0.001% chance of being fertilized, so the OP’s warm butt wasn’t creating an environment for the egg to thrive in. They were merely keeping it warm until it went bad. And as you already know, rotten eggs are the absolute worst.