Why did I become so underweight? I thought this was suppose to make you big?!

"I actually been eating only 1000 calories or way less everyday, is that maybe why?"...Not "maybe" DEFINITELY. I don't know who told you it was okay to eat that little, but they lie. YOU (not anyone else, because anyone wanting or needing to lose weight to be *healthy*, the operative word here, can negotiate a bit less like 1300 or 1200 and no less than that) need no less than 1500 a day...you have a serious problem. Really. What do you eat, lettuce, bread, and water? Get help.

Okay, I apologize for that insensitive statement. However, you did not specify that. You said "I think I have a eating disorder because eating over 1200 calories seems to much to me." but you didn't say if you felt it was physically too much, as in you CAN'T eat even if you want to. So I'm sorry for saying what I said.

However.

"But I thought it gets you fatter if you eat 1000 calories or less?" I wonder who or what could ever put this idea into the mind of someone who isn't a kid. How could any remotely intelligent adult think this? I get the terrible feeling you have less than honest people in your life that tell you less than honest things. Otherwise, perhaps in addition to seeing a therapist, you should also take a health class (though I though they had those in middle school at least). I'm sorry, but you need tough talking to because if someone could make you believe that eating less calories would make you gain weight, then people obviously need to be a little more firm in giving you the truth instead. If you think you have an ED, please go see a doctor, then a psychologist instead of asking strangers on Yahoo! Answers.

I'm pretty sure you have an eating disorder here. I would go see a GP. Eating 1000 calories is VERY unhealthy and you've put your body into starvation mode (affecting yourself in the long run!) and created lots of health problems. You are not healthy at all. You should be eating 1500 calories a day if even to maintain your weight but since you've probably slowed down your metabolism a lot, start with 1200 and work your way up. If you don't change now, things you do in the future will become a challenge - having kids, exercise, everyday activities, etc.

Take your body weight, multiply by 10 and then add again your body weight to this value.

For e.g.:

If your body weight is 115 lbs

115 x 10 = 1150

1150 + 115 = 1,265 calories burned in a day through BMR

You need to eat 1500 calories a day minimum for your height. If you're under 20, closer to 1800.
You are anorexic, get into therapy now so your whole life isn't dictated by a fear of food.

you should eat 1,200 o 1,500 calories a day. Just start eating meats, milks, & cheeses.