please help

i’m 15 and my whole life i’ve been called too skinny and anorexic, up until about 2 years ago. now i don’t get called that and i feel fat. so i’m not eating as much so i’m just wondering when does it cross the line into an eating disorder like anorexia. i don’t eat all day, only drink juice, until around 6 when i eat dinner. and when i eat dinner, i ensure the portions are smaller than normal. please help