I totally know how you feel. I haven't been there for a while thankfully, and recently I'm managing to eat properly without purging (well, for the most part), but it's something that weighs on my mind. My best advice is what I did: try to exercise regularly and eat healthily (without denying yourself the occasional treat). If you're doing this, you'll feel less guilty and less likely to purge, plus the exercise and good food can give a lift to your mood.
If you do purge, try not to let it get you down, simply take it one day at a time. If you go from doing it daily to doing it every other day, to once or week or whatever, well that's progress. Take little steps. Also, can I ask, do you binge and purge or do you purge without binging? Also, do you calorie count?
I know someday you'll have a beautiful life, I know you'll be the star in somebody else's sky...
But why can't it be mine?