Due dates and how far along?

Kirsty
I'm feeling really confused by all of the info I'm getting, glow decided I'm due on the 31st Jan but I have no idea where that is coming from! I did a <a href="https://play.google.com/store/apps/details?id=com.glow.android.nurture">due date calculator</a> and it says 19th of Jan which I updated and glow now says I'm 5 weeks 4 days, can anyone clarify? My LMP was 14/4/16 and I ovulated around 5/5/16. I just want to follow its development!!!