Hi, Sammay, when they gave you your first due date, of May 17, the assumed conception date would have been around August 25, which actually lines up pretty nicely with your 44-day cycles (we ovulate two weeks before our next period, not two weeks after our last one) and may have even been how they computed the due date. If your baby was born a week early on May 10, his assumed conception date would still be August 25. A baby being born early does not change when he began. Even if your baby was born at full term on May 10, he would have been conceived on August 18. As you can see, these dates have nothing to do with July 31. If the guilt over the sex is bothering you, your best bet is simply to resolve to make your boyfriend the happiest dad in the world forever. Don't dump on him your guilty conscience, just put a sock in it and be a good girlfriend or wife forever and a good mom, and make him a happy, happy man. That's how you atone.
My periods are normally about 44 days long