Sara, I am so very sorry. I am so glad that you got a chance to say goodbye. I know that there is nothing I can say to allieve your grief. Fluffy loved you, and you loved him. He will live in your heart forever. Prayers go out to you today.
Sara, grief does not get easier. It's the most painful experience there is. Yet, to heal we must go through pain. Death is part of life, as is birth. Fluffy has not ceased to exist. He lives on in another dimension, and he may be closer to you than you realize.
Sara, dwelling on the past will just make it worse. You did the best you could for Fluffy's welfare. This is what you have to focus on. The decisions you made, you made with love. And Fluffy knows this and understands. He is on the other side. Fluffy is with mo now, take comfort in that, and one day you will all be together. Keep Fluffy in your heart, as you do mo.
The loss of a pet is very painful. Sometimes there are mistakes by the medical profession, both with pets and humans. So many of us have gone through this. But, in the end, we all did the best that we could do with love and the best of intentions. So, as you go through the grief process, just be at peace, knowing that you did everything you could.