TTC baby #2

Catherine

Hi ladies, I finished my period three days ago. I wanted to find out on which day i should start taking my ovulation tests I just have five tests.. The App states that my ovulation date is the 19th how can I more or less work is out.. Should if I take my cycle duration and subtract the 14days I get the 16th as my ovulation day.. 😬.. Ek I started taking PregVit vitamins is it okay?