Electrolyte imbalances can cause muscle twitching like those you describe. I thought I'd mention that because you said you over-use laxatives, which, I'm sure you know, can cause electrolyte imbalances with over-use. I'd take this seriously and tell your doctor. Your heart also depends on the correct balance of electrolytes to function properly........and at all for that matter. This is how people with long-term eating disorders die suddenly of cardiac arrest. Is your doctor aware of your eating disorder? At least let him draw them to check.