Posting for a little insight!! My last period was March 25-30th. My next estimated fertile window…

Posting for a little insight!! My last period was March 25-30th. My next estimated fertile window was April 9-14. I had super light pink, sometimes brown spotting from the 10th-15th. It was never enough for a pad, or even tampon. What do you think the reason for this was? I've had ovulation spotting before and it's only been for one day, and only there when I wipe.