To answer your question Nicole, follow what your body tells you.
Remember that feeling hungry means your burning fat, but also remember that if you don't eat enough, your body will stop metabolizing food. this means two things.
First, it means you won't burn any fat at all, and will be completely exhausted.
Also, it means that any food you DO eat will be almost completely stored as fat.
In short, you will gain weight instead of losing it.
Instead of limiting calories, I'd suggest first up-ing your exercize.
It's the biggest thing you can do, because it burns fat the fastest.
More food and more exercize together can cause a much better result than starving yourself.
I can't emphasize enough that you shouldn't eat too little.
I've been there.
If you're getting sick or dizzy or light headed, it means you are eating too little. You're only gonna gain weight that way.
I'd also like to say that 100lbs may be too small.
Try talking to someone you admire.
Find out the weights of some celebrities around your height and such.
You might even ask someone who you think is really pretty how much they weigh. I know it can be akward, but I bet you'd be surprised at their answer.
Don't let this get out of control.
An eating disorder is not a fun thing to have, and it's like a drug.
Once you're hooked, you're hooked.
Be smart.
Be positive.
Realize that the way you look shouldn't determine the way you feel about yourself. There are things bigger than the outside of a person.