I know EXACTLY how you feel!!! My wife and I had to take our Darling little Dog (Sasha) to the Vet, to have him put down, on the 21st of January, 2019: It was the worst and saddest day of my life!! My wife and I both had tears streaming down our faces, as the young female Vet. put our little baby boy (he was 15 years old) to sleep forever!!!
It was awful!! I cried more for our baby boy, then I did when my little brother and only sibling died!!
And I still want our little baby boy back!!! Sometimes I still feel like I'm going to lose my mind!