12 days late bleeding

Hello! So I was 12 days late for af and thought I maybe had a faint line but wasn’t convinced...I then “came on” on the 12th day heavy bleeding lasted 2 days now it’s like a bit of red discharge not a lot at all and I’ve been so tired and have been sick, I took a pregnancy test just to rule it out completely and it was negative any advice is so appreciated thanks guys.