RE: I regret getting a puppy and I don't know what to do.
I'm sorry you're feeling stressed. I agree with the others and what you said about this dog being innocent and needing a good home. You need to be honest with yourself and your boyfriend about all of this.
Honestly, I'm a little concerned about the relationship you have with your boyfriend because the way you made it sound was that he pressured you into taking a dog and said that he's giong to keep it regardless of what you think. While that is, of course, his choice, it definitely doesn't seem to me like you guys are at a place in your relationship to be co-raising anything.
I hope I'm wrong and just read more into it than I should have and everything works out for the three of you.