Just found out I'm pregnant at my 6 week postpartum appointment 😳

Well ladies...I am THAT woman. The one who 1. Had sex before the 6 week mark and 2. Was told I'm pregnant at my postpartum appointment. My husband had a vasectomy when I was 6 months pregnant with baby #3. At 8 months pregnant we got the results of his semen analysis and were told he was good to go. At 3 weeks postpartum we had sex ONCE...I began bleeding after so we decided to hold off. Well, I got paranoid and asked him to get retested and last week they told us he had recanalized and there were some live sperm in his sample but not a lot. So...that one time, even with low sperm count resulted in baby #4. Because of when I had sex my doctor was able to estimate my due date and says I'm already 5 weeks because of how you're considered 2 weeks upon conception and we had sex 3 weeks ago. Im shocked. My babies are going to be 9.5 months apart 😰