sojuorn .... I can't add to anything said or even remove your grief, but I will say one thing...
YOU WILL recover. Eventually, you will remember the good times, the fun times you had with your little friend. You will not remember the sickness, the pain, the failing, the death. You will remember the quirky things he did, the soft/tender moments you shared, the just being a friend with another species of animal.
Your cat has passed to the other side. Whether that other side is nothingness or something bright and special, you were there with him in the end. Besides the life you appeared to have given him while he was here, nothing more could have been asked of you.
Stay strong...keep him in your heart and this (the pain, not the memory) will pass...best wishes.