My last period was around March 4th or 5th. I had sex with my current boyfriend around the 15th without any protection. When it came close to time for my period to come I was having sharp cramps and I really didn't think anything of it. I always get cramps before my period comes but these where different. We had sex again around the 1st of April and almost 2weeks later my breast got really sore. I noticed my nipples had gotten a shade darker so I took a pregnancy test. I found out that I was pregnant. I'm having the hardest time deciding if I got pregnant around the 15th of march or is it more likely to get pregnant when your period is about to come. I know that doctors can be off.

No way to fully know if it is within a couple weeks. So you will have to get a DNA test after the child is born to fully determine who the father is for sure.

While it can vary from woman to woman, it is more likely you got pregnant from the sex you had on the 15th than from the time on the 1st. It is not as common to get pregnant right before a period is about due. Many women will get some cramping in early pregnancy, often about the time their period would be due.

Before I went to the doctor I thought that he had got me pregnant when we had sex in April. I had started to get the symptoms almost two weeks later and I was late. When the doctor gave me a December due date it really shocked me that the baby was actually going to be almost a month earlier than I had expected. After hearing so many times that the doctors can be off, I had to ask. Thank you for helping me out.

Also, when you have an ultrasound they will be able to tell you about how far along you after measuring the baby. Ask the ultrasound tech it is actually built right into the machine. They measure the femur and head to determine how far along you are. Good Luck and Congrats!

According to Nagele's Rule if the first day of your last period was March 4, you are technically due on December 11. This is the most common computation of due dates.

Now, an ultrasound is more accurate as they measure certain bones of the baby, such as the femur, to determine gestation. However, conception is truly nothing more than a guessing game.