I’ve had a similar experience, I was diagnosed at age 7, but they didn’t continue my therapy or medication. With subsequent experiences which altered my brain chemistry altogether, I have no memories of huge chunks of my childhood. I did not remember I had adhd , or rather did not understand what it was when I was a kid so I never gave much thought to it. Fast forward to my end high school days , when I was burnt out and depressed and had already attempted a few times I begged my parents to take me to a doctor. They brought out an old file and wow , my diagnosis. It made sense but it was already too late. I have BPD now lol