Bless you my friend. I've been there way too many times myself. Buried them all.
Most went from natural causes....the one I loved the most I had to put down. That was the day I quit being selfish, and dug a hole big enough for a 100lb dog in the back forty on a cold and wet November night. Longest day of my life. I know your loss...believe me.
Nothing is ever lost so long as we're still here to remember.