I don't know your case, but judging for this message maybe you depend too much on your brother, u rely more on what he says or does than on yourself, and that can't be good. As for if have bulimia or not... If u have the "routine" of throwing up once a week, it seems something is going on, and I guess u do it for the same reason u cut yourself... And these 2 sympthoms indicate that something is wrong, and that maybe that underlying depression is not over, and all the stuff that leads u feel that way is still there.
I'd try to talk about it with someone, ur parents or friends, and I'd go to a therapist or something, because if u don't do anything to overcome that hidden stuff it ¡s not going to go away by itself...
Take care
