Though I'm sad for what you are going through right now, I'm glad that you've brought the weight issue and bulimia up. It's a VERY common misperception, but in fact "in order to be classified as bulimic the person must be of normal or overweight."

You can find the DSM-IV criteria that psychiatrists use to diagnose bulimia nervosa is as follows:
(1) eating, in a discrete period of time (e.g. within any 2 hour period), and amount of food that is definitely larger than most people would eat during a similar period of time and under similar circumstances
(2) a sense of lack of control over eating during the episode (e.g. a feeling that one cannot stop eating or control what or how much one is eating)
B. Recurrent inappropriate compensatory behaviour in order to prevent weight gain, such as self-induced vomiting; misuse of laxatives, diuretics, enemas or other medications; fasting; or excessive exercise.
C. The binge eating and inappropriate compensatory behaviours both occur, on average, at least twice a week for 3 months.
D. Self-evaluation is unduly influenced by body shape and weight.
E. The disturbance does not occur exclusively during episodes of Anorexia Nervosa.
**Specify type:
--Purging Type: During the current episode of Bulimia Nervosa, the person has regularly engaged in self-induced vomiting or the misuse of laxatives, diuretics or enemas.
--Non-purging Type: During the current episode of Bulimia Nervosa, the person has used other inappropriate compensatory behaviours, such as fasting or excessive exercise, but has not regularly engaged in self-induced vomiting or the misuse of laxatives, diuretics or enemas.

Anyway, most people know all this, but I include it because it took a few read throughs for me to see that there is no mention of weight loss, or being underweight. When someone is underweight and has bulimic behaviors they are considered to be the binge-eating or purging type of anorexia (most people just think of the restrictive type of anorexia).

Although some people purge everything that they eat compulsively (not only after a binge), or purge after ingesting very small amounts of food, this would not be considered bulimia.

Not to say that this isn't eating disordered behavior -- this is where the EDNOS (eating disorder not otherwise specified) is used, or the anorexia binge/purge type if underweight.

Also, people who are bulimic may alternate between bulimia and b/p type anorexia, the latter of which could involve fasting or compulsive purging of all food ingested. This would explain the occurance of large drops then gains of weight in a bulimic.

These would be the cases where people lose weight, as far as I know. Bulimia by definition only involves purging after a huge amount of food is ingested (a binge) and the purging is done to "compensate" for the "excess" calories consumed, not to rid oneself of a normal, recommended number of calories.

I'm on meds now that control my appetite, so when I do "binge" it's not a real binge (just something like a piece of cake, that I wouldn't allow myself to have for fear of gaining weight). Before this my binges consisted of consuming 4,000-8,000 calories in about 20 minutes.

I gained 30lbs while bulimic; now I'm EDNOS and have lost 15. I still consider myself bulimic, because of the purging, but really I'm not since I don't meet either of the 2 binging criteria.

Sorry for the rambling, I hope some of it was helpful at least.

Jessie