Looking for a mom/ son story!!!

I am trying to find this story it was on Reddit and is about a mother that has to sit on her sons lap in the backseat of the car whilst the dad is driving. (I think they were driving to the sons college) The mom and son end up having sex right behind the dad without him knowing, it’s about 3 parts I think can someone please help me find it.

Source: reddit.com/r/Erotica/comments/lwzcwq/looking_for_a_mom_son_story