Just because you make your self throw up once in a while does not automatically make you bulimic and I say this coming from personal experience
You're bulimic. Any time you force yourself to vomit, there are potentially serious risks. This is not the way to lose weight.
binge eating or purging is never a good thing to do...once or twice a month doesn't qualify as bulimia however you are setting your self up with some bad habits that could lead to it down the road... do you find your self doing it more when you get stressed or if someone makes a comment about your weight???