how effective is this to get pregnant?

Hi,
Welcome to ehealthforum,
If there is ample vaginal wetness present, then the sperms can swim up and enter the uterus and tubes to fertilize the egg if present in your system (this will result in pregnancy if the incident occurs around your ovulation time and especially if there are no vaginal or cervical infections present). The egg once released from ovary can stay alive for 6-7 days and sperms once inside you can stay alive for 3-4 days. Wait and watch for your next periods. If you do not get your periods within 10 days of expected period dates, or if you get abnormal periods, or if you develop symptoms suggestive of pregnancy, you should consider visiting your gynecologist for thorough examination (to confirm pregnancy related changes/signs in body) and blood/serum HCG level test (to confirm/rule out pregnancy accurately). Take adequate rest. Drink plenty of water. Maintain healthy diet and lifestyle.
Take care.