Do i absolutely have to get teeth extracted for braces?

My orthodontist said that he might have to pull out 4 teeth.... I'm 17 so I'm getting them quite late. I do not want a sunken face no way. I already got a small mouth I dont need it to be any smaller. Are there any alternatives? Please do not say Damon. I'm getting braces on NHS so they're free. I do not have 3k to fork out. :(