You want to watch Dr. Russel Barkley's videos. He does the best job of explaining ADHD as an executive function deficit, not an 'attention' deficit. https://www.youtube.com/@russellbarkleyphd2023

There is a world of difference between slow study and a severe brain impairment that blocks the ability to function normally in the world. For example perhaps there is a minor focus or motivation issue where you would rather be doing something else and so find the studying less of a priority. A person with severe ADHD may forget what they were doing while they are actively engaged doing it. Imagine driving a car and your mind drifts and you begin to focus on something at the side of the road now completely unaware of what is in front of you as you continue driving forward without reservation. A person who struggles to study, on the otherwise, does not suddenly become unaware they are holding an open book in front of their face.

If you are concerned that you might have ADHD I recommend an evaluation by general physician.