Late pregnancy

I have been nauseous for the last week and I am eight days late on my period. I had one day of very heavy bleeding about 10 days before my period was due. I am constantly having mild cramps about 3-4 inches below my bellybutton and have had them for maybe 2 weeks. hpt's are coming back negative. I do have ovarian cysts on each side, the larget one is 2 centimetres. I was wondering if cysts can cause missed period or similar symptoms to pregnancy or if the hpt's could be false negatives?