My Oreo was the same way!!! I had about a good month with him 24/7 until i started working full time. And when I started working full time (8 hours a day) .. My boyfriend would always take care of him in the morning, and then he'd leave too. but always would check up on him every hour or two.
Oreo would just sit in the same place we left him. not move (maybe to pee/poo or eat) .. and when i got home i'd feel so awful although he'd always be soooo happy to see us.
I could tell Oreo was lonely. and that's why I got Ginger. It was the only way! and he's so much happier with her now, they always play together and he does still miss me when i'm at work. but now he stays at my boyfriends house or my house and is never alone

so yay!
Maybe it is time for another companion?