Amber - I'm so sorry for the pain your're feeling. I'm glad you had the good years with him and made his life a great one. It's so cool that you could stay with him till the end so he didn't feel alone.
When I had to have my kitty PTS, I planted a perennial plant outside as a memorial to her. I call it the Tigey bush. (her name was Tigey) I think of her almost every time I see the plant but now it doesn't hurt anymore.
Be nice to yourself and if you can, get some time just for you.
Hugs...