Had an accident last night! Help!😩

I’m three months pp and breastfeeding. Last night husband and I think we had a slip up and I’m mortified. My first birth nearly killed me and the second was the closure I needed to end that chapter of life. He was scheduled for a vasectomy because we both agreed our family is complete. But now I’m terrified I’m pregnant again. I haven’t had a pp period yet either so I’m even more lost because I don’t even know how to tell if I’m pregnant besides testing randomly! What are the odds of being pregnant breastfeeding before your period starts? Should I be this concerned? I’ve heard breastfeeding can help prevent pregnancy but I’ve also heard you’re even more fertile..