Had unprotected sex 6th august, period started 17th of july, when can i do a pregnancy test? and will the 4 pill "gynera" every 12hrs to prevent it?

May be: If you are a 19 year-male, you cannot get pregnant. If you are asking for some one else, do a pregnancy test if she misses her period by 4-5 days, or after August 17. If the result is negative repeat the test in 4-5 days. Use first morning urine and follow the instructions for the test carefully. If you do not wish to be pregnant, use contraception all the time, every time. You may consider implanted contraceptive, or IUD. Practice safe sex. Get HPV vaccine.