ADD/ADHD is a developmental disease so you would have it as a developing child and it wouldn't have gotten better as you grew up. The adult aspect is that things are different for an adult than for a child, one doesn't have/do the same tasks and as an adult, one may have gotten use to coping with the symptoms in a way that could mask them.

It doesn't sound like, with your class-length focusing skills that you have a problem, sounds like just a lack of general interest. Focusing requires desire and practice and not liking to play board games or go to movies is mostly just an interest thing; I don't do those either.

Good luck with all your finals. I would try to shift how you study, instead of just reading the dry text, outline it or take notes, write about it, get your other senses involved or study the material online from other sites that are more interesting than the textbook?