My ADHD experience is VERY like yours! I was EXACTLY the same as a child/teenager, then got diagnosed in college at about age 21.
I think like that when I’m depressed. I look at everything negatively. Things people do all have a negative motive, things people say have a negative meaning, things I think are all a general ‘doom and gloom’ topic. I find my hormones seem to affect this a lot, but sometimes it’s just if I’ve been working too much or stressing out too much. I start taking 500mg Tryptophan before bed for awhile until it goes away. I read ‘The Mood Cure’ and got a lot of helpful advice from it.