Weird period...

So I'm kinda new to this whole period thing ? I recently got it. My last two periods have been exactly from the 22nd to the 27th but this month I still havnt gotten it, I think they said your support to be irregular for awhile (and if this is true how long?) I have had mood swings for the past two days and more personal craps and a light discharge, is there any telling when I will start, or if it will come soon? Thank you for your advice!