Up-date on my eating

I posted a message on here regarding my eating and weight not too long ago. Ok, when I posted weighing 97 pounds was the weight that I remembered from my last weighing session. Today I went into a shop and spotted a scale... I pulled it off the shelf and stood on it. I now weigh 84 pounds, at 16. I am 5'3 too. It was a shock when I read it but felt like an achievement. So yep, this means I have lost a lot of weight... somehow. Im unsure what to do at the moment. Is it healthy? People are always saying I am too skinny, I need to put weight on but I just dont see it. The cantine person said "Emma you are wasting away" but when I look down at myself I look like everyone else, healthy average weight... the scale says different. 

Let me know your thoughts, 

Emma x