I am so sorry for your loss and I know how you feel. Last Saturday we had to put down my "therapy" cat. People don't realize how attached we can all become to our animals. Just know that your kitty is going to be in kitty heaven hanging out with mine. They're gonna be fat and healthy and never get full on their food. They're gonna play and be waiting for you. Unless there isn't a flow of time there, and you're already there with them.
I know it's hard but you have everyone on here. You will get through this and if you ever need anyone to talk to, I'm here and so are many others.
(If I offended you about the kitty heaven, I'm very sorry. But know they're better not being in pain)