I have been waiting for my period to arrive for a week now and it's still not here but I have had PMS symptoms for the past 4 days. I had the flu last month for a long time along with a chest infection, would this delay my period? Or have I miscalculated when I was due? I also was under quite a lot of stress, just 2 or 3 weeks ago and this is just making me more worried. I have never had unprotected sex.