I'm so sorry for your loss. As time moves on it definitely gets easier to deal with the pain of it. I lost my first Yorkie just over 5 years ago. I still think of him. he was only 5 months old and somehow someway ate rat poison.
I only had him 2 months and took him everywhere with me. He was only 3lbs. My little Stuart. I came home one day to find him covered in his own urine, feces and saliva. I rushed him in to the vet but it was too late. He died 20 mins later.
I was devastated. I went to every person's house I knew and asked them about rat poison, but never confirmed where he could have eaten it. I only can guess that my neighbor was using it around his garden which was up against the chain link fence that ran b/t our yards and Stuart may have gotten it from our own yard through no fault of our own.
I have Dexter and Fletcher now and I adore everything about them... I love them to pieces and they are my babies. I STILL think about and miss my baby Stuart. I wish I he had a longer life with me.
My heart and prayers go out to you. I know how painful it is. (((HUGS)))