Sounds like the symptoms I had before I went to a doctor and found out I had Crohn's disease. Although I didn't just wake up one week and not be hungry, it was more gradual. I remember having nothing but a soda and being full all day, meanwhile I was loosing more and more weight and feeling like I was wasting away. I'm about 5'6" and my weight dropped down to about 120lbs, I could look in the mirror and see my heart beating...pretty crazy!

It might be something else, but if these symptoms persist it would be wise to see a doctor, especially if you start throwing up after you try to force yourself to eat.