My ovulation time frame?

Heather
So Im trying to figure out when I might have ovulated this month. I was on birth control for about 3/4ths of a month before I started spotting very, very faintly (something I have never done before while taking birth control previously.) Two days after stopping the pill I started my period but it was only four days instead of my usual full seven during a 30 day cycle. Do you think I would have ovulated 14-16 days from the day my period actually started or from the day I had my breakthrough bleeding?