Forgetting a sentence immediately after reading it

Hey! I’m 23[m] and went through the first 22 years of my life with undiagnosed ADHD. I’ve probably spent a total of 8 hours or so studying during the 12 years of school. Which is basically nothing, not even the bare minimum (not counting the panicked reading and memorizing right before exams at school).

I discovered my passion for reading a few years ago but that was still very difficult to do. I read in English which is my second language (though I’m very good at it) so I was a very slow reader and was never able to create the habit, so a single book took me months to finish because I’d quit it for a while. There was also the brain fog issue, where you read a sentence/paragraph and can’t process what it’s saying so you have to re-read it.

After being diagnosed last year and getting medicated, the brain fog was lifted and I find it easier to sit down and read, and focus my brain power on the damn WORDS that are entering my head. But now I realize that a lot of times when I read a sentence or paragraph, I comprehend what I’m reading while I’m doing it but then I immediately forget what I just read and can’t repeat it back. I have to re-read the sentence. I used to think that’s just the brain fog and lack of focus, but it seems like something else is the issue. Could it just be that I don’t have any practice? Is that normal? I’m trying to increase my speed so I don’t waste so much time on one single book (even though I read multiple at the same time) but this is making me doubt my abilities. It took me more than half a year to finish Crime & Punishment and I don’t think I want to take that long for every book.