Your going through alot right now and have so much going on inside your head that you feel you need a release and youve always got that release from purgeing.
Please try and give yourself a break,your being very hard on yourself.
Unfortunely heart attacks can happen suddenly in anyone with an eating disorder as permament damage to the heart is often caused.Your t sounds like she warning you that the meds make the risk even higher.
Be care ful but dont beat yourself up if you have a slip up.A slip up is a slip up thats all.You can always start again.
Take care