I would say yes you are,I would think 120 a good weight for 5"5, if you feel okay and are eating Healthily it maybe you are a slender Frame are the rest of your Family slim?Do you eat 3 meals aday ?
My family is not slim at all. I eat 3 meals a day and a snack.
Do you worry about your weight? Do you purposely try to lose weight? Are you afraid to gain weight? Have you ever had an eating disorder? Sorry about all the questions but it will affect the answer to your question. And if you don't mind me asking, how old are you? Age is also a big factor.