so I haven't been on for awhile due to taking care of my two year old and my 7 month old! :) I have…

so I haven't been on for awhile due to taking care of my two year old and my 7 month old! :) I have a question though I was supposed to start my period on Dec 13 but didn't actually stay til Dec 18 when I go to see when I start again do I got by when I was supposed to start from last month or when I actually started! cause this month I haven't had a period yet!