Like I said in the question, Dexter has been just yelling at us for a few days, and today, was sleeping on my mums lap and just woke up, started yelling, and jumped to attack. He didn't do anything, just backed up and looked kind of scared.
We have two cats, him (4 years old, male, neutered) and Maggie (7, female, neutered). They get along great. Both of them are ill-equipped to make babies, but sometimes Dex will get too excited and mount her. He always looks so confused, so we just pick him up and set him down.
He HAS been having trouble peeing in his litter box. We've tried it all: different sands, box types, puppy pads, everything. He just wants to pee on the TV. We've sort of got this under control now.
We haven't been to a vet yet, but if he doesn't start acting like himself again soon, I may get him checked out.
I just don't know what to do. He's always been the sweetest little boy, even as a teenager kitten. I'm really worried that he might be ill.