CDR come on- you aren't freaking fat! *slaps*
Just kidding about the slap, but not about you not being fat. At 90 pounds you will look like a sickly chic that needs ALOT of help. Trust me- being really skinny doesn't aways make you more attractive. If anything, losing that much wieght will turn people off to you because that will be all you can think of, it can be addictive and eventualy you can die from it.
Seriously, talk to your parents. If you think you're fat and are starving yourself they NEED to know.