The best way to determine if we are pregnant is to visit the OB-GYN and to get yourself tested if you have missed your period or if you think you could be pregnant. Pregnancy can be confirmed from the first day of the missed period and if so you would have conceived your child two weeks prior to this. But it also depends on the test that you take.
There are certain home pregnancy test that can give conclusive results about 4 or 5 days prior to your period. This is because in the first few weeks after implantation their hCG level tends to double every 48 or 72 hours from a very minimal amount of 5 mlU/ml. By about 7 days after implantation there is about 50 mlU/ml of hCG in ones blood stream. Thus it can be said that by about 7 or 10 days we can determine whether we are pregnant by using the home pregnancy test.
If your menstruation is regular every month, you can have a pregnancy test once you missed your period in the following month. You can buy a pregnancy test kit and have a sample of your urine in it. Pregnancy test kits measure the pregnancy hormone (B-HCG) which is above 25 when you are positive in being pregnant.
Women who are not pregnant have a minimal amount to none of this hormone as this will become present and it increases when a fertilized egg is present. It is advised to get a pregnancy test kit to confirm your pregnancy and visit an ob-gynecologist for more tests and to give health advice.