First, I am sorry for your loss, I lost my cat a couple years ago, and my husband and I were very sad when it happened. We both cried. On the other hand, however, when my father was sick and my YM was in Indiana, he would never ask me about my dad's health. That is why I did not let him know when he died but weeks later, when he finally asked.
Second, it could have been a cat, a gerbil, or a pet cockroach, it was your pet and you loved it, and that should be enough reason for him to be considerate of your pain.
Despite the lack of consideration on his part, this should not be reason to break up a relationship. I think that you should definitely wait until you are calm and less in pain, and have a conversation with your bf. Tell him that you feel that he has not been considerate to your feelings, and again, it could have been a cat, or a goldfish, it was dear to you and that is all that should have mattered. It was YOU who was in pain, and YOU who needed comforting, not people to enterntain. Only have this conversation when you feel that you can deliver your points without getting emotional.
You know it's love when the pain of being apart is greater than the pain of being together.