How to stop......help starting to worry now!

Ok so I am starting to get a little concerned with the amount of weight I am losing. I weigh less than 2 of my 5 year old. I have lost more weight than I currently weigh. I am uncomfortable in bed because I have no padding between my knees. My tailbone is uncomfortable all the time. (I watched a show last week where a lady had hers removed because it stuck out so much after weightloss) I just walked past a mirror at work and I couldn't believe how skinny my arms look. I almost look skeletal. I have no idea how to stop this and my next appointment isn't till the 30th April.
I took a pic of my arm, to show you how it looks:



Any ideas on what to eat to bulk up. And don't say chips, chocolate and full cream milk cause I do all of that now!