Calculating first period after miscarriage

Chelsea

Need your input! I recently got my first period after a miscarriage in November. I had very light spotting from 14th to 18th and then what seemed to be my normal period from 18th to 21st. What day would you consider the beginning of your period on the calendar, 14 or 18?

It obviously changes my days of ovulation and we are TTC, would appreciate any help and opinions <3