ADHD is an addiction to procrastination in a sense. It could be that you missed diagnoses at a young age due to being intelligent enough to cruise through school and university with little effort, so your problem was never picked up as you never suffered any serious negative effects from ADHD due to your intelligence and ability to get tasks done quickly.
That's basically what happened to me. I'd be able to do an assignment that would take people several days, in half a day. So I'd be able to procrastinate and delay up to the last minute and still manage to pull through, usually not with great grades, but I'd pass. I always thought I was lazy, and never considered the fact that it could be a deeper neurological problem.