Confused about my weeks!?

I recently switched from a Galaxy s4 to a iPhone 5, well on my galaxy <a href="https://play.google.com/store/apps/details?id=com.glow.android.nurture">Nurture</a> had my weekly mark on a Tuesday, but on my iPhone it has me set on a Sunday and it's saying I'm 14 weeks today? Idk just wondering when I'm really changing weeks lol. My due date is set correctly also.