What happened?!

What happened?

I was just told I am underweight, but i dont feel it && dont see myself like it.
I was just dancing to this song I did about 10 times and the song is 4:50 min
I was working really hard and i started to sweat alot (the song is really fast) and i started to feel really dizzy and my back started to hurt really bad and i felt like everything stopped working in my body for a moment and i fellt as if i was going to barf and i did my ears started throbbing and my feet go numb.
Everything i just told you except the everything in my body stiopping i still feel what happenend?

3 weeks ago
my legs started are shaking

3 weeks ago
I am not extremely underweight i think she said 15-20 lbs

3 weeks ago
I am only a kid

3 weeks ago
I am flexible!! gosh!!
I have been doing ballet and jazz for 11 years

if you're underweight and you're exercising hard like that for 40 minutes, you'll feel like that. Why? Because when you exercise, your body uses the food you eat as energy. If you've got an empty stomach, your body will take from fat reserves in the body. In an anorexic, there isn't any fat so the body has no choice but to start eating away at the muscle for energy. If you're underweight, chances are, you don't have any fat. That means when you work hard like that, you'll pass out from lack of energy. Here's a good chart http://www.myfit.ca/weightheightchart.ht... I'm 5'3" and 140. I'm at the high end of the healthy weight. Look yourself up.