Stop begging every day, as that will just make them immune to your request. Consider that they will bear much of the responsibility as far as vetrinary bills, food bills, etc., and will be ultimately and legally responsible for the new dog. Also, in a few years you will graduate from high school and be off to college. Fiove years seems like forever right now, but it is a short part of a dog's lifetime. Most dorms do not let you take pets with you - those are few and far between. So once again, the new dog would be your parents' responsibility.

Once you have acknowledged all this in your heart, and thought about it long and hard, if you still want another dog, sit down calmly with your parents and discuss what, if anything, you can do to prove you are responsible enough to care for it. Set clear goals, and see if you can reach a compromise with them.