Im 16 i have period problems!! i need helpp!!!?

okay im 16 and i don't get on my period right and im so worried im just 5.4 about 130pounds and im so worried because if u get on ur period right u can't get pregnant or hv a baby im so worried about my life how can i fix this by trying to get on my period right idk what 2!!! im like crying for help and the Doctor gave medicine and she did say is was gonna be fine in a month... But i didn't! the medicine didn't help me at all.... im so worried any doctor out there can help me plzzz!!!!!!!!!!!!!!!!!