did you ever start letting him out and play with him when he whined? because i don't know why he started whining all of a sudden when he didn't use to. (if you let him out when he was whining, then maybe he learned that if he whines, then you will let him out)
i know what you mean about breaking your heart to leave him like that. the only way i can leave milu and ignore her whines is if i just leave the house right away. if i stay home and hear her whine, then i give in and let her out to play.
you will just have to be firm and not give in when he whines. ( i know it feels like it's impossible!!!) perhaps get some new toys, and rotate them. (dont put all his toys in the bathroom with him, he'll get tired of them, instead, put a few different toys in there with him each day)
also, you can try to walk him or make him chase a ball to burn off some energy before you leave in the morning, so he will be tired and sleepy when you are leaving.
give him his favorite treat right before you leave, so his energy will be focused on that when you are leaving.
good luck
