It’s definitely not just you! I forget things all the time, and as you said, it’s not just THINGS. I am also the person who will forget what I’m doing in the middle of a task. I find on the days when I have to be super focused it’s worse afterwards. It’s like brain has hit a wall and can no longer function properly, it’s maxed out. Some of the tools I use to help are using Siri or Alexa (I think they were created by people with ADHD because they are just so darn convenient lol), using reminders on my phone (or making lists on my phone) or calendar, and not dismissing them until it’s done. Don’t have time right now, ok fine then it will be snoozed every 30 mins to an hour until it annoys the living daylights out of me so I get mad at the pop up interrupting me and finally do it. I also use timers for small appliances and lights so they turn off and on at the same time every day, that way I can’t forget because the timer does it for me. One other thing I find that works decently (most of the time) is to ask someone to remind me of something, it doesn’t matter if they do or not just the act of saying “don’t let me forget X” will help me remember.
Good luck! If you ever find a way to not forget what you’re doing while you’re doing it, I would be interested to know.