Well, I'm not sure if a pregnancy test could lie 5 times to you..It is probably the stress and being sick that is keeping AF away. If I were you, I would try to take care of the symptoms you are feeling, wait another week to see if AF comes, if not take another HPT, if that is neg still, and still no sign of AF, Call your doc for a check up and maybe a blood test to see what is going on with your hormones. Good Luck!
My period last month was a week late but I was feeling every symptom in the book. (There is no real difference in symptoms between being pregnant & PMS.) I took 2 hpt's that came back negative, so I just trusted the results. And then voila; af came.