I think I might be anorexic.I drink a bottle water everyday.I eat under 300 calories everyday.I've purged a few times.

No way to tell with such little information.
If you have serious health concerns of this nature then you need to raise these with your own healthcare practitioner.

How old are you? Healthy adults eat 2000-3000 calories a day.

You are malnourished.

You need to see your doctor very quickly, your behavior may seriously injure you.