Personal experiences?!

Hi y’all! I’m going to the doc soon, but just want some insight if any of you have gone through same thing. I was 12 days late on period as of yesterday and now I’m bleeding but it’s mostly brownish In color with some red. At about 8 days late I took a test and it was a vvfpl and then tested 2 days later with negative and then the next morning after that was negative. Could I have ovulated late? Just a late cycle (my cycles are pretty regular)? Chemical pregnancy? I’ve heard some women do bleed while pregnant.

Sorry for the long post, but thanks for reading!