Brandon’s bully has found a strange alien device and uses it to torment Brandon and his mom by swapping their bodies and forcing Brandon to obey the bully’s every deviant desire in Bully, too explicit for Amazon and only available on Body Swap Stories or Smashwords. Preview here.
I remember reading this one back in the day and loving it.
Any chance you know the name of the model?
Unfortunately, this was before I started keeping track.