Pet Loss - I just can't seem to move forward

My dog died very suddenly about 3 weeks ago and I'm deeply struggling with the trauma and grief. I still cry everyday. I still feel sick.

trigger warning for details of his death

My fiance had this dog since he was a puppy and for the past 2 years we've lived together, the three of us. But even before then I would help to feed, groom, walk, and care for him. (Fiance and I have been together for 11 years now, dog was almost 12 years old)

I thought about him every day. Due to a seizure a few years prior he was clearly showing signs of dementia (pacing, confusion, sometimes walking as if he's blind but walking normally most other times, etc.). Our furniture and our lifestyle was adjusted to make him as comfortable as possible.

One day we had gone out for errands and to spend time with friends. We had left him at home a number of times on the 2 years we'd lived here. We found him long gone, having gotten stangled by some cables for our Internet.

It was horrifying to find my baby like that. I would have never in my worst nightmares imagined this would happen. But I feel so stupid for not preparing for it. It seems so obvious in hindsight. I would have managed the cables better if I thought it might be an issue.

We thought about him all the time. We were constantly talking about ways to make him healthy and happy. After his seizure a few years back he used to throw up regularly and have days where he was lethargic and dizzy. With our effort he had been healthy for months. His diet was good, he was more alert than ever, he was as active as a senior dog could be.

I am heartbroken. The morning we lost him my fiance said he'd live to be 30 and I joked, "Do you really want to deal with him for 20 more years?"

I do. I really wish I could.

I just don't know how to feel better.