I'll echo what everyone else is saying. You
really need to eat more, for several reasons.
(1) Food provides nutrients. You can tell by the way you feel that you're starving yourself.
(2) You don't want to make your body think that there's a famine--that could make you more likely to gain weight once you start eating more normally.
(3) It's tempting to want to lose the weight quickly, but part of what you need to be doing now is setting the stage for lifetime maintenance. Even if you could do 600 calories for weeks or months (which would be damaging), you'd be setting yourself up to gain the weight back after leaving the state of perpetual deprivation.
Be nice to yourself. It's not a race. The weight loss journey is a time to learn and reflect.
Hang in there.