You can't undo it at this point. Panicking does no good. Obviously, don't take any more. I would bring the package to your health care provider just in case. But try not to panic. If you are talking 2 weeks after day 1 of the pregnancy, the fertilized egg was probably not even implanted yet, so it would not have been sharing your blood. People take/do all kinds of things before they know they are pregnant with no ill effects. I took half a pack of birth control with my first, and my son has yet to grow breasts :). Don't beat yourself up about it, just be as healthy as you can for the rest of the pregnancy.
Oh, and you may be able to check the ingredients online. Drugs have different grades for risk during pregnancy, and you may find that the risk is quite low. Unless it is X (known teratogen, like chemo drugs) I wouldn't worry a bit.