Do i have an eating disorder?

i am 5'6 and i used to weigh 127 lbs a week and a half ago. i now weigh 120 lbs...my target weight was 120 but i'm still not happy and i want to weigh less. i eat consistently throughout the day, but my eating has gotten to the point where i wonder if i will gain weight by eating half a cup of whole grain cereal for breakfast. and for lunch i had a tofu hot dog (45 calories) without a bun and i thought it could make me gain weight. am i going to keep losing weight or will it ever stop? am i okay? thanks!