Please help!

Okay so I have about 3-4 different period apps. I found out I was pregnant March 27th. My last period was February 29th. According to all of the apps I’m Due December 5th but I’m

Getting different results. One says I’m 4 weeks 6 day, another says I’m 4 weeks 4 days. They are all saying I’m 4 weeks but just different numbers on the days. I’m so confused. I’m also trying to figure out when I conceived because when I put in the due date, nothing matches. Please help me makes sense of this!! TIA 🤞🏾