 [ Symptoms ] what can cause a period to be late  i am 25 have always had regular periods and i am now 3 days late i had protected sex 4 days ago i have been under a lot of stress and not sleeping well could i be pregnant or what else could cause my period to be late [ Disease ] sorry i misspelled peri menopause not pre also if your not any of the things above in the other message and your period still wont happen talk to your doctor about provera a medication to bring on a tardy period