I’m horrible with movies, too. TV shows are alright, because they’re usually much shorter. Sporting events are also suspect – sometimes I need to get up and pace around when watching sports.
I think it’s the drugs. When I came off my medication, I was able to watch movies fully again, and binge on TV shows. Going back on the drugs stopped this again. Of course, there is the possibility that the drugs permanently alter you after a certain amount of time…