I also have ADHD but wasn't diagnosed until my 30s. I started drinking and using drugs in high school, then when I discovered speed and coke I became seriously addicted, using every day. Years of pain, fear, self loathing and trauma followed. Ruined finances and relationships. Many attempts to get clean, rehab, AA, NA etc. Now been clean and sober for 8 years and my ADHD is being treated properly with Concerta.
My psychiatrist says if I was probably using speed and coke to self medicate my untreated ADHD and I think she may be right.
I now have a stable and happy life, with a good job, a wonderful husband, two cherished cats and hope for the future.
The problem with coke, mdma, speed etc is that the first high is the most amazing, and after that you're just chasing that first feeling but never getting it. I could only get clean when I finally realised and accepted that I would never get that feeling again. But I wasted 20 years chasing that unattainable high.
Drugs are a dead end and are not worth it.
There are far more beautiful and amazing feelings and experiences to be had living a sober life than with street drugs.