I would like to know wat precautions you used during your contact as it would decide the chances of you getting pregnant.
First thing is to confirm your pregnancy
for which you do your urine test for pregnancy with the help of home kits available for the same. Incase it is positive before taking a medical abortion
(abortion using drugs) you need to get an ultrasound
which will help you know the site and size of pregnancy. Before taking any abortion procedure you have to get your ultrasound and consult a gynecologist personally as abortificients have risks of severe bleeding, pain , shock and failed abortion. So you have to take these drugs only under supervision of your doctor. If your pregnancy is not beyond 7weeks she would advise you the required drug. But for now without knowing all this i cant prescribe you the drug and dose.
Incase your pregnancy test is negative, it might be just a delay in menses. In that case you can use progesterone tablets
for withdrawal bleeding like regesterone
. Dose and time your doctor would let you know.