I heard my parents "doing it" last nite?

Ok my friend is over and its probally like at 10:30 or like 11 idk and i went in the kitchen to say good night to my parents but when i was trying to open the door it was locked then i hear the bed going up and down and my mom moaning and my dad just grunting.disturbing. i run back to my room to get my friend and im like i think there doing it so we go back and lesson and my mom is moaning LOUDLY and im like HOLY CRAP this is the first time i ever experienced my parents doing it i tried looking for condoms or something but nothing so i think its safe but i know they were each other. i know this is disturbing but i dont know what to do and this is my step mom who got here last week shes from china and im like just knowing her. I dont think this is the first time they did it cuz i know they did it when my dad went to china iwas searching and exploring his iphone and i found a picture of my stepmom like half naked WUT SHOULD I DO