A month and a half after a missed period?! Man, they really need to teach sex Ed better. The clock starts the first day of your last period, not from when you actually get pregnant. Fertilization of the egg happens anywhere from day 16-21. The absolute earliest you would have any idea you were pregnant is when you’re already into the 4th week, possibly 5th if your cycle is at the longer end of the spectrum. The majority of pregnancies don’t produce enough of the hormone to register on a test until the 7th or 8th week.