confused about my due date

Okay so my last period was September 6 , and my usual cycle is around 30 days if that matters .  I had sex on the 18 and there was a 7.6% chance of pregnancy glow said . And than on the 24 there was the highest chance and we had sex again .  But the other app said if I got pregnant on the 24 my last period would have started on the 8 and it didn't . Can someone help me figure out my expected due date? I know I'm pregnant for sure but the doctor didn't give me a due date yet .