First, you have to be sure if you are pregnant or not. You can perform a home pregnancy test because lack of menstruation is not a aure sign of pregnancy. Every pregnancy includes lack of menstruation but not every lack of menstruation means pregnancy. If the pregnancy test is negative you are not pregnant. If the test is positive you can visit your gynecologist for ultrasound confirmation of the pregnancy.
If a pregnancy is confirmed, there is nothing you can take to get rid of it. You can get rid of the pregnancy only with a medical abortion performed by gynecologist.