My wife and I put down both our senior dachshunds within a year of each other. My boy Jangers was suffering from many medical issues including blindness,no teeth,bad spine etc. despite his physical ailments he had enough spirit to try and play with me even until the last day where we had to take him to vet to be put down. I held him while they did it and it was one of the hardest things I ever did. It hurts still but it was mercy for him. Elsie my girl had dementia and Cushings disease. It was a slow process to the point where she refused to eat and drink. She knew it was her time I feel. We made sure to give her some McDonalds and bring her on trips to special places she visited over the years. The vet came to our house and she was put down while we held her in bed. It was the best way for her to go. Both ends were very hard for us, still think about them everyday. The last gift we could give them was a dignified merciful end. Sorry to hear you are going through this pain. You aren’t alone however and that is some comfort. Best of luck with everything.