My ticker says I'm 3 weeks and a few days. Is this right? I have another app I'm using saying I'm 4 weeks. And that the day my period is ddue would be my 5th week. My question is, why are they all different? And what do you ladies go by? The first day of my last period was July 19th and I have about a 13 day lp. I think I ovulated on the August 1st. Most calculators say I'm due April 24th or 25th.