welcome to HCM,
kindly mention the history of your previous menstrual cycle, where they regular or there was a variation of 30 to 35/40 days.
since you have already got 2 pregnancy
test negative and have not got your periods yet.
the best way to get rid of the confusion is to do an ultrasound, better will be a transvaginal ultrasound
. this will rule out pregnancy and see for any pelvic pathology if present.
you need to visit an OBG for your treatment.