What happens if i dont have my period for a month ?

i Got My period when i was 10 and now im 12 . And over theese moths i have not been getting my period . i have 1 month without my period and what is getting me very uncomfortable is that im skipping periods to much i have skipped periods 3 times already and im scared people tell me its normal because ir irregular but i already had my perios for a year and a half !!!!!!!! so isnt suppose to all regular right now !!!!!!! and NO GUYS im not PREGNANT cuz i havent had sex.