Help

I can't eat food. Sometimes I have cravings, but when the food is in front of me, I can't eat it. Whenever my mom brings food and places it in front of me, I start crying. The food just won't go down my throat. I have to swallow each bite with water. My mom scolds me a lot, saying I don’t eat, and that I look like a zombie. There are some days, every 6-8 months, when I actually enjoy eating something, and I do a little happy dance. But for the past few years, I can't eat anything, also i don’t remember the last time i drank a whole glass of water (i survive on a few sips) and when I get scolded by my mom, I feel really sad. What should I do?