I am so so sorry to read about your poodle. Words cannot help the pain that you feel but I feel that I understand your feelings. I too have a Mini Poodle..Julie. She is our world too. She is very sick & I feel the pain & loss that you do. I have tears in my eyes for your dog & you. Try to think of all the wonderful times you had with your dog.
My heart goes out to you.
That is one of the saddest things I've read here. I'm so sorry for your loss. :-(
He obviously had internal bleeding, but without a post-mortem exam by your vet, there is absolutely no way of knowing what caused it. He may have had cancer (unlikely but not unheard of), ate something that caused internal damage, or even been poisoned by an outdoor plant, snake, insect, or purposely by some sicko. There are just too many things to consider to know for certain without an exam.
Assuming he was fine when you went to bed last night, the only saving grace here is that he didn't suffer long - if at all. As traumatic as this is, please try to remember that Cuddles had far more good times in his life than the trauma at the end. Whatever happened to him, it sounds like it was so severe that even medical help may not have saved him. Allow yourself time to grieve. I hope that when you're ready you will be able to share you life with another lucky dog. :-)
I just want to extend my sympathies. It is always so hard to lose a member of our family. sara