My cycle is always the same, heavier the first day and eases up the next three. now it's super light but on time took a hpt it's negative. what's wrong?

Happens sometimes: Many women have occasional variation of their mucus discharge, some spotting between periods, a heavier period, a lighter period, a longer or shorter period, or even a missed period. Having one or two of these symptoms doesn’t necessarily mean there is a medical problem, but a visit to one’s primary care or Ob-Gyn doctor is a good idea if symptoms are persistent, recurring, or worrisome.