As Lori mentioned, see a doctor asap. Weight loss can be diet related... or it can be indicative of a serious medical problem. The only way that you can know for sure is to get it checked.
On the diet related side, the simple answer is: eat more. The reason that you feel so bony is that you've likely lost a lot of muscle tissue. While protein intake is important for muscle maintenance it is not the "be all end all" for maintaining muscle. Actually, significant muscle loss is very common for low carb dieters (many tend to have a very low energy intake due to appetite suppresion as the diet progresses). Anyway, in the meantime, try gradually increasing your intake of carbs (try to stick with unprocessed stuff... fruits, oatmeal, yams, etc) and/or healthy fats (salmon, nuts, etc).
And, you should see a doc about this just to be sure.