How many days after...?

The first two weeks are when you are ovulating and such so you're really not pregnant until 2 weeks after conception. I found out when i was 3 weeks pregnant, so i found out very early. I, like you, was also unsure of when my last period was and it is nearly impossible to pinpoint the exact date of conception but the doctors can give you a round about as to when the think it happened. Just keep in mind, its probably not %100 percent accurate, but it is likely near that time. Good luckl!