Hi... my age is 19 years,always my periods are regular every month I had my periods but sometime dates are change 2 or 3 days extend... I had my period on last month 16 date... but yet I don't had periods,is this normal?. any concern/worry about it? please tell me.. n I a mot marrid and not had sex never

This is not uncommon. Your periods can change frequently. If you've never had sex, there's no need to worry about pregnancy.

Yes, first there are different amount of days in a month, so they will never always be on one day, like 16th, that would actually not be regular if they were.

But give or take a few days, even missing one every now and then can happen