The language used in the post is what bothers me most. “The dog was annoying me.” Is that actually what you said?
You knew he was attached to his dog when you got together with him, right? For some people, their pets are like their kids. Can you imagine if he said to you “the kid is annoying me, I don’t want her in our bed anymore.”
What I see – and probably what your boyfriend sees – is that you’re selfish and manipulative. To turn an argument over a dog into an argument about an imagined future pregnancy is a manipulation tactic. You need to seriously evaluate yourself, and get some therapy.
And break up with your boyfriend, for his and the dog’s sake.