disappointed and baffled

After several HPT, two different brands showing BFP(testing daily beginning 5 days before expected AF), I started bleeding 4 days after my expected AF. First it was very light pink and barely spotting, then at night it got super heavy and bright red. The following day(yesterday) in the morning I soaked a pad in less than a hour, then it started slowing down. Today, I'm spotting(not flowing) and it's red not pink. I've had three children and this has never happened to me before. My fiancé and I are pretty bummed and confused 🤷🏼‍♀️