Should I end my friendship with my best friend?

He said I was going to be going to Maine with him ALL YEAR, but now he decides to take someone else who he hasn't known half as long. I have done everything for this kid, helped him with girls, money, Cigarettes, and life and he still decides to backstab me like that. When my friend didn't have a soul to talk to I was there for him and helped him through thick and thin. But if I end the friendship, then I have no friends.... So what should I do?