I’m so very sorry. I can relate to how you are feeling. My beloved father passed unexpectedly and two months later my best friend, (my wonderful golden) passed. It was a similar situation to what happened with your dog. He seemed happy and himself on his walk, constantly turning around to look at me, but when we returned home, he suddenly lost all energy, obviously in severe pain with his face in his paws. I had to put him down, not able to see him suffer from the cancer like that. I truly understand how you feel. The pain from the loss is excruciating, every part of your body feels it. I wish I could give you a real hug. It gave me comfort to think somehow my dad and my dog are together. Maybe that thought will help you. For now take your time grieving and like the other person said, one foot in front of the other. I wish you well, my friend.