It could very well be ADHD. Depression is certainly another possibility, but if your symptoms are more or less consistent throughout life, then it makes ADHD much more likely.

It's definitely a bit tricky. Depression can cause problems with attention. But also: ADHD people have depression at much higher rate.

> When I was young I used to look at the watch compulsively to check what time it is and I never went late to an appointment.

Lots of ADHDers come up with all sorts of coping mechanisms. It's one of the reasons the test misses a significant chunk of ADHD population.