Period ❗️HELP ❗️

Hey guys i am worried I haven’t had my period in a month and I really can’t be pregnant can someone tell me why this might be. I can’t be pregnant because never had sex and only 13 got my period last year I searched up and some websites and almost all of them say that in the first 2 years you might miss a month or two and if it is three go to a doctor I am not sure if this is true someone help me