I thought that, but those thoughts are invalidated by the few memories I do have of being extremely productive, completing that project or task and feeling wonderful as a result.
No, for me, I spent about a year reading books about adult ADHD. After getting a couple of opinions, it appears that I am. However, I didn't fully believe it until I got to talking to other ADHD adults, and I recognized some of the quirky, fidgety, talking over others things that I always tend to do and I was like "yup."
However I don't like how the stimulants make me feel and I already am a heavy coffee drinker, so I am experimenting other ways I can cope: earplugs and headphones with white noise, blocking visual distractions, letting my manager know of my condition (big positive, at least for me), and I am now experimenting cutting sugar completely out of my diet.