Haven't had a period..

Ruth

Okay, so my period is late by 33 days (eve tells me) anyways I know for a fact I'm not pregnant I went to the doctor for some other health conditions and they took a urine sample it was negative Ive also took 2 on my own before the doctors visit. I'm not on any type of BC but I plan to get on it soon. I do skip every once in a while but I should have started by now.. any ideas on what may be causing this?