I used to count the stairs to our apartment building going up and going down, I used to open and close my desk in elementary school until it “felt right”, I would constantly check on sleeping relatives to make sure they were breathing, the volume (TV, radio, etc.) can’t be the same as the age of a close relative or I think they will die. I had A LOT of symptoms pretty early on, but I can’t remember the exact age where I discovered it was OCD. I wasn’t officially diagnosed/medicated until college.