There could be many reasons for why you are finding it next to impossible when it comes to stopping your purging habit. You need to figure out a way to end the purge-cycle and you need to put steps in place that will prevent it from happening again in the future. To do this you need to focus on more positive coping methods that will help you fight the urge to purge. One of the reasons why you cannot stop is because you are more or less unwilling to put in the effort that is needed to turn things around and end your need to purge once and for all. You need help and you need to have a team of people behind you who are willing to support you and who are willing to get you from point-a to point-b.