A relationship can change and evolve over time for a number of reasons, however if such changes are occurring suddenly or out-of-the-blue then you might have a reason to be worried.
Adding a pet to a relationship comes with a lot of new responsibilities and makes the relationship more serious now that you both have to take care of a raise an animal together.
Maybe I've watched too many scary movies the last couple of nights leading up to Halloween, but dreaming about all sorts of spooky things like dying is way worse than any movie.
Have you recently said "yes"? Right now your head is probably spinning, and you are flipping through every wedding magazine that you can get your hands on.