Suggest Treatment For Irregular Periods

Hello, my name is Makaya, and I have an irregular period, and well I am very worried I am pregnant, I have took online pregnancy test (OPT) and they have came back negative and I am underage to buy a pregnancy test, I have not had sexual intercourse at all, and I am still very worried. I know I might sound crazy, but I just want answers from smart people, but I have a worrying problem, but will you help me out, PLEASE!