28 or 30 days period

So, my period is either 28 or 30 days in.. past few weeks I have been feeling off. Been dizzy a could of times, nausea, back ache, and all those PMS/ Early pregnancy signs.. if I follow the 28 days period to start, I am late by 2 days but if I follow the 30 days one, my period is due tomorrow .. I normally get horrible back ache and cramps before my period but today, it’s oddly quiet .. feeling scared to test cause I don’t want to be disappointed.. is there any one that has gone through this? And when you did test, did you get a positive result?