•You can’t get pregnant if you’re both virgins.

TRUTH: Alas, you’re just as likely to get pregnant if it’s your first time or your fiftieth.

•You can’t get pregnant if you’ve never had your period.

TRUTH: You get pregnant when you ovulate, and sometimes that can happen right before you have intercourse even if you haven’t had your first period. Pregnancy before even getting a period is entirely possible and entirely common.

•You can’t get pregnant if you’re on your period.

TRUTH: Menstrual cycles are very unpredictable and vary, especially in teenagers (that means you, friend), and a girl can easily get pregnant when she is on her period.

•You can’t get pregnant if you are on birth control.

TRUTH: It happens! A lot. Birth control pills/shots will give you a good edge, but there is no surefire way to prevent pregnancy, and they don’t protect against STDs!

•If you do it girl-on-top, you can’t get pregnant.

TRUTH: Sperm are tough, and they designed to fight gravity. It doesn’t matter what position you’re in, if you have unprotected sex you can get pregnant.

•If you leave you both leave your underwear on you can’t get pregnant.

TRUTH: If this one were true, condoms would be made of cloth. It’s a lot cheaper than latex. Even if there isn’t any skin to skin contact, sperm can and will get through fabric and most other barriers. The materials that they make condoms out of are the same materials that they make rocketships and submarines out of. Trust the NASA engineers and go with a condom, not your undies!

•You can’t get pregnant if he pulls out.

TRUTH: My little sister is proof that you can! This one is similar to #6. Sperm don’t just come out in one big finish at the end, guys can ejaculate during intercourse as well. All it takes is one.

•Jumping up and down after sex will cause the sperm to leave your body.

TRUTH: On average, about 300 million sperm are released after each ejaculation. Even if you managed to get a few out, there are still millions more. This one is a no.

Source: teensource.org

•You can’t get an sti from oral sex

TRUTH: During oral sex, you can give your partner your STI and you can get theirs. Not all STIs are transmitted through oral sex, but some are. For example, if your partner has a cold sore (oral herpes) and performs oral sex on you, you could become infected with herpes in your genital area.

•peeing/douching after sex protects against pregnancy

TRUTH: When a male ejaculates, the sperm travels through the vagina into the cervix, and then into the uterus. Urine is released from the urethra, not from the vaginal opening, so it does not come in contact with sperm. Washing or douching will not prevent pregnancy due to the speed of which semen travels into your cervix and the fact that water can’t reach the uterus. In fact, douching can actually push sperm up farther up into the vagina. Douching also causes an imbalance of healthy bacteria on your vaginal walls and can put you at an increased risk of contracting a vaginal infection.

Source: iwannaknow.org