I know exactly what you are going through. I, myself feel guilty that I didnot do enough for my nearly 16 years old cat Shebba. She had hyperthyroidism and anemia. In Sept. 2009 after her yearly check-up and shots, Shebba weight 8.7 lbs. Her vet wanted to do blood work on her , I declined because of money reasons, I was had huge vet bill for my dog,already I could not afford it. She the vet also never told she suspected there was anything wrong with my cat. So with that I made decision that probably led to my cat demise. If the vet would had told me, she was worry about something was wrong, I would had done it and some how found the money. She just started to change so fast, she would not kitty litter, instead use the rest of the house as place for her solid waste,, which became more liquid and soft. She began to pee on the edge on the kitty litter box. I chuck it up as old age. She continued to eat and drink as she normally did. Sometime she would vomit after eating moist food of salmon. I thought there was nothing wrong, probably bad salmon or it was left out and got spoiled. I never once thought she was sick. The week after Thanksgiving she weighted 6 lbs,yet she didnot looked it, by Christmas her weight was about 4 lbs. She was sick and I should of noticed that. I should had taken her into the vet ,then but I didnot. I waited one extra week by that time she weighted only 2 1/2 lbs. The vet said she need a blood tranfusion, just to survive. I want to, but I feel that my Dad, who was with me, had pressure me out of it. I made that decision to put my fur baby to sleep and today I still hating myself for it. Hyperthyroidism was so treatable she could had lived much longer, if I got her to the vet earlier, she became anemic because of the weight lost and flea who preyed on her weak state. All easily preventable. I wrestle with my emotions over and over every day. I think I took her for granite, that was always be there, health, not as sick as she truly was.