6 days late now spotting

Sam
hi, I'm after some advice. I took a first response test on Thursday - it showed up the control line and a pink dot where the positive line would show. I rang the helpline and they suggested it is positive and to re test. I started to bleed the day after. No regular AF symptoms as I normally get horrific painful and heavy periods and extremely sore boobs. This time nothing. Periods very light and no pain etc. I did a clear blue test on the day I started bleeding and it was BFN! What's going on? Any advice