Pregnancy tests are usually only accurate from the day that your period is due or afterwards. If you only had sex a few days ago it will not be possible to tell if you are pregnant yet.
If your periods aren?t regular it is probably worth talking to a doctor or nurse to decide whether or not you need to do a test.
You can get pregnancy tests from doctors and contraceptive and sexual health services plus some young people services. You can also buy them from chemists and other shops.