I feel you man we had to put down one dog recently, same feeling no kids so you make the dog a kid. I baby the other dog constantly now, like I give it double attention. Like we've mentioned before a drug doesn't always help this feeling. A mild stim sometimes does more for mood than a powerful AD drug. And they really can't totally remove loss, no drug can. It's about what gets you closest. Time will help, although it doesn't feel like that when your in tht tick of it.
Are you sleeping man? That will compound any depression. And diet too, I'm not saying go get totally fatty, but I thought ice cream helped me too even if it was only food. Some comfort dishes your mom used to make maybe? Learn how to take up one of her hobbies or interests online.
I'm probably just shooting in the dark but I feel for you and hope you find something that fits your need bro.