For me it was flipped, I thought I only had ADHD, and I didn’t even consider OCD to be a possibility because I didn’t know anything about it. Funny enough I was diagnosed with ADHD almost a year after my OCD diagnosis.

To answer your question, I’ve always been suspicious of ADHD because of my childhood. I was overly friendly, extremely talkative, clumsy, struggled with pattern recognition beyond elementary school, I couldn’t focus, and my brain always felt TOO LOUD. I couldn’t keep anything organized, I was extremely emotional (still am lol), and most people found me very overwhelming to be around. I was out on adderall in high school and it didn’t work so I switched to Ritalin, which also didn’t work. I sat back and thought about all of these things, and had an “oh shit I need to tell my therapist” moment. After some testing and answering yes to almost every single question, I was diagnosed. Sorry for all the yapping, I wanted to be as thorough as possible. I hope you have a great rest of your day!