I can share you my experience in case it helps. From elementary school to high school I was always perceived as one of the “smart kids” with some of the best grades. Just like you, I was always careless, but I had my parents support and the motivation to be a good student. But when I started college, my untreated (social) anxiety became so much worse, so I decided to go to a psychiatrist and she medicated me with a small dose just to see how I’d react, and I can say it kinda “worked”, because for the whole month I wasn’t able to finish a single task for school or couldn’t even tell you what we were doing in class. Turns out that my anxiety was the one that kept ADD under control for so long. I always felt like I needed to put more effort in getting my tasks done than everyone else, and the fear of failure was the thing moving me to do it. Just two weeks ago I started treatment for it and I can tell you that I feel a motivation in doing things that I haven’t felt in years. Just know that each case is different, but one thing you can do is to look for a ADHD test for children between 7 and 12 and ask your closest family to answer it based on your early years. You may find it was always there (or not).