As you say you've suffered from anorexia in the past, I'd say ask a trusted friend/friends to tell you if you get too thin.  It's easy to start seeing something in the mirror that's different from the reality.  And if you don't like ephedrine then stay away.  I personally don't like the feeling at low-dose, makes me anxious.

Finally- if what I've suggested STILL doesn't work (unlikely, but some people do have slow metabolisms)... then you've gone as far as you can go.  Just maintain that diet, maybe the weight will actually come off very slowly and you just hadn't noticed that it was doing so.  But if it doesn't, and you're still a stone or two over the weight you've been aspiring to... well, then it would be time to accept that that is your natural weight.  How your body wants to be.  Don't make yourself miserable just to satisfy the media image of how you should look if you can't healthily and happily maintain the current model.  In this case, you would be best served to love yourself for who you are. 

Good luck