I just put up a story about my 5cats i lost in the space of a year. My last one i feel responsible for, if i'd gone out into the garden and brought him in he'd still be here, he wasnt well and was old and wasnt supposed to be outside and yet i watched him, partly because i felt sorry for him being cooped up in the house. I still wish id gone out and brought him in, and its a year ago now. You aren't to blame for what happened, you're as much to blame as i am. I was away when my other cat was ran over and i felt angry for not being there, but being there wouldnt have changed what happened. But i really do know how you feel.

I can relate to how you are feeling. My cat Susie passed away in July. I started to think she was ill, but waited several days to act. I kept thinking, "Maybe she just has a passing flu," although a cloud of dread hung over me for 3 days. When I saw her condition was not improving, I still kept an appointment to get my hair cut. While there, I was a nervous wreck. I told myself, "If she still seems ill, I'll take her to the vet when I get home." After getting home, she was still not well. I took her to the vet and then to emergency care that evening. It turned out she had multiple things wrong, including a blod clot in her lung and a heart condition that was causing her lungs to fill with water. Her condition was not treatable and she was unable to breathe without receiving oxygen. She was put to sleep the next day. I feel angry and ashamed with my actions. I could have spent more time petting her and loving her, but I delayed action and then left her alone for a few hours while I went to the hair salon. It is hard to forgive myself for this.

To the left is a picture of Susie, my sweet cat I just wrote about above.

I know how you are feeling. I lost one of my cats (Speckles) on the 6th April this year, we were away on our honeymoon at the time.
She had had a Ceasarean Section to deliver 2 kittens, she had had one naturally, 1 born by C section was dead, the other lived. This was on the Saturday (day after our civil partnership ceremony), we flew off to America on honeymoon on the Sunday and had a cat sitter come in once a day to check on them. On the Wednesday the cat sitter rushed her and our other female (Penny) to the vet, and rang us in America to tell us to ring the vet urgently.
when we did, we found out that Speckles was seriously ill, had been found collapsed at home that morning. Penny had had one kitten and no others. It was decided to give Speckles 24 hours to perk up with antibiotics and a drip and then see how she was. Penny was given a C-section and delivered 3 more kittens, 1 died shortly after but 3 (including 1 born naturally) survived.
The next day Speckles had perked up and it was decided to operate to find out what was going on. Speckles died under anaesthetic. They carried on and found out that her bladder had exploded.
I feel so guilty, if we had been at home, we would have noticed her condition going down hill and noticed that she hadn't passed urine since the op, and maybe she would still be with us.
Penny raised 5 kittens (her 3 plus Speckles 2).
We felt such a void, despite having 3 other cats, that we decided to keep one of Speckles kittens.
Facially he is the spitting image of his mum and we have to do a double take when we see him. His nature however is nothing like her. She was always a bit of a loner, not too woried about cuddles. Lucky (he was lucky to be born as he was the one by c-section and the vet thought they were dead in her) is the exact opposite, always looking for affection and cuddles, like he is making up for what his mum never gave us.
We still miss her and always will.
After my Dad had my dog put to sleep in 1998 and I never got to say goodbye I always swore I would be with them when the end came. So feel guilty every day for not being there for her.