Hi name.n and welcome to our forums
I can relate to how you feel completely. It's an empty feeling and for me it is one based in guilt. Pets (or any animals) to me are at human's kindness or not.
I feel so guilty when I've had to take animals to the refuge. Years ago I lived behind some shops and there was this female feline that used to regularly have kittens. She was reasonably 'tame / friendly'. Her kittens were feral. It was so difficult for us, one of the kittens had broken it's leg and we had to restrain it and take it to the local vets to have it put down. The next was another one of the ferals that we became friends with - when we were able to get close we picked it up and took it too the refuge. It sat and watched us leave - saying 'you betrayed me' (that's my thinking).
The good news from this story. We took the mother feline to the vets and had her desexed. She remained as the local feline that roamed the neighbourhood. She was gorgeous and visited us regularly.
I have grieved for all my lost animals throughout the years. It is hard when they have shared so much of your life. But please think about - it's okay to grieve for animals, that it's is very healthy and it shows your compassion and empathy.
You are not ridiculous!! You are human and caring. That's so lovely to hear. Animals rock. And while one passes (as they do because we tend to live longer than them :(, unless you have a cockatoo or turtle), our grief is hard. I must confess their life circumstances (e.g. death or moving on to others) are so painful at times. Grief has a number of phases that have no order and that one can go through, at different times.
Be kind to yourself name.n. Caring for an animal the way you do shows your beautiful character.