What Causes A Delayed Period And Negative Pregnancy Tests?

Hi



I am 8 days late on my period. HPTs are showing negative. I have had nausea, increased discharge, hot fluses, increase in passing urine, I had a slight show when wiping last Tuesday. Also am very tired. I had miscarriage at 20 wks last October and periods had returned to a normal ( for me) 31 day cycle. Pleasse can anyone advise? am scarred that something may seriously be wrong, something that can cause infertility.