Mom with home tutor

So...when I was young my parent hired this guy as my tutor ... Now I'm realising there was something else than my grade that were raising " his dick " for my mum ;) .... I was too young to understand it then but now it's clear ...mom would come stand beside me checking my progress . Her hand would be on my back and his " my tutor" hand would get in her ass ... I noticed few times but didn't think of it much ... He would call him in kitchen to check if the tea is good 😐 i would hear giggles for few mins 😬😬 .... The tutoring only lasted for 4months but those incidents years latter has stuck with me that basturd* ... The worst thing is I get hard thinking about that idk why