Something like ADHD is notably difficult to diagnose because its symptom behaviors are things that other people also experience, just less frequently or severely. Everyone has limited executive function, spaces out, forgets things, becomes restless, procrastinates, etc. to some degree. So it's difficult to notice the point where it crosses the threshold of interfering with a healthy life.
It is entirely reasonable to wonder if you've been misdiagnosed as having it, just like a neurotypical person may wonder if they have ADHD from normal experiences. It's not like we have another life to compare ours to.