I had sex on the 4th september & used a condom. i then had unprotected sex on 11/12th september. i am now pregnant and due 9th june with approx conception of 15th/16th sept. did the sex on 11/12th sept lead to the pregnancy?

There are a few methods for estimating due date. 1). Using the date of last menstrual period (start date) subtract 3-months, then add 1-year. 2). Estimate by size of the baby on ultrasound. When estimating conception date, you may start with the first day of your last menstrual period, then look add 10-15 days after that. If paternity is in question, it paternity test would be most accurate.

Based on your due date, the below website states that your most likely conception date was 9/16/2021. That you used a condom on 9/4 and the conception date is 12 days later, fatherhood likely belongs to partner # 2. Then again, you can always take a paternity test. ref: calculator.net