Rhythm method?

Gabrielle • Married my best friend 9-20-14 & mommy to a beautiful little girl ❤️
So I have been off bc for 9 months and my soon to be husband (in just 3 weeks) and I have used a combination of pull out/ rhythm method but I'm extra cautious. This time he did not withdrawal on the last day of my fertile window.. What are the chances of pregnancy and should I worry? Cycle doesn't start for another 9 days..