stupid question

Kate
So the first day of my last period was 2/23 so according to Glow I am 4 weeks 5 days. But I was using opks and got a peak on 3/14 so probably ovulated on 3/15. If you count back two weeks from conception to get time I would be 3 weeks 6 days. So since I ovulated on CD21 and not 14 because I have a 35 day cycle and not 28 day cycle the traditional timing doesn't work for me. Should I just go by ovulation? How do I change my due date on Glow?