Sex education is clearly so bad that I'm seeing grown men totally misunderstand basic anatomy and sexual biology. So here's a few quick points that everyone, male or female, should know;

1. We don't get to decide when our period is, how long it is, or when it starts. Most women have periods once a month and it lasts 3–7 days, and are roughly predictable for most of us unless we're stressed or unwell. They usually start from the age of 9 to 14 and stop after menopause (usually late 40s and 50s). You can't control whether you're bleeding out or not, it's like an open wound, and yes it fucking hurts. The only alternative to going through this every month is constantly taking hormonal contraceptives: something many of us strongly avoid due to the impact on our weight, mood, and health. While I'm on this point, just grow up and get your girlfriend tampons. You're a child if you're disgusted by it.

2. Starting a period does not mean a girl is ready to have a baby: almost all girls who give birth before 14 have further complications or maternal injury (prolapses, permanent infertility, pelvic injury etc). They have to have caesareans in most cases; those in poor countries often die in childbirth. Their little bodies haven't developed an adult pelvis and the ability to carry a 6–10lb baby. There's a reason most aristocrats waited a few years into strategic medieval marriages to consummate them.

2. A woman is the most fertile in the middle of her cycle. But you can absolutely get her pregnant outside of that week, so don't risk it, ovulation is rarely exact. Tiny things like diet, stress, climate, sleep and even mood can cause shifts in your androgens and even the most well reviewed of 'natural' apps fail. If abortion, fatherhood, or Plan B aren't options you're prepared to think about, you absolutely shouldn't be rolling the dice on unprotected sex at all.

3. You can get a woman pregnant even if you pull out, and even if you think you didn't ejaculate until you were outside of her. Sperm release is not always consistent with final orgasm. It might decrease it considerably: but it's never a dead cert and there are enormous numbers of unwanted pregnancies from this 'method'. If it worked reliably, we'd have no need for contraception at all. Again, slap a condom on it. If nothing else, you don't want to get an STI.

4. A baby is created when only YOUR sperm reaches a woman's zygote. That's the only way it works, unless we're talking IVF which you'd definitely remember happening and paying for. There is none of her previous partner's DNA in that baby: it will have half your genome and half her genome. Any sperm in her body would have died long before you rocked up to be jealous about it. But what if it was a threesome? It's still going to be genetically yours or his. Always. Without exception. There are no kids secretly walking around with 23 extra chromosomes from the milkman.

5. No, a woman doesn't 'absorb the DNA' or 'permanently hormonal bond' with a man who takes her virginity. The body does not 'store foreign DNA', it does not form a 'oxytocin bond' with the first man who sleeps with her, or any other weird sci-fi nonsense you've read about. There is no science at all saying that male DNA traces come from sex, zero. In fact, you should be *very* worried if you're substantially carrying the DNA of another human and you're not pregnant, a relative, post partum or post bone marrow transplant, because your immune system will probably try to destroy it as foreign or cancerous and make you very sick. Also, DNA traces exist on all surfaces: a head louse that threw up on your scalp would leave his DNA. Your healthy intestine has millions of foreign microbes and bacteria in it with loads of weird DNA. But you're not going to be impacted by your ex's DNA at all. It's just not going to happen. You're being weird.

6. Only you need to orgasm (or climax) for a woman to get pregnant. A rape victim didn't 'enjoy it' if she gets pregnant. Nothing about the female orgasm really contributes to the reproductive process, apart from making it pleasurable enough for us to bother doing it. If it wasn't, I think we'd all give men a very wide berth in the bedroom.

7. Lesbians can get pregnant and want to get pregnant. See above.

8. Women aren't 'evolved' to fall in love with whoever sleeps with them, while men have evolved to feel nothing at all. This is particularly stupid so I encourage you to think about it. Does your first girlfriend from college still adore you? Is she mad with lust and begging you to come back to her? Almost definitely not. And not because she's a thot or a hoe, just because you were both just young people experimenting and she's probably married or engaged by now. Similarly, if men didn't get emotionally attached in physical relationships, they wouldn't commit suicide over, have mental breakdowns over, or straight end up murdering the woman who didn't want to date them anymore. Do men typically enjoy casual encounters more? Sure, they don't need to worry about being raped or getting pregnant anywhere near as much. But sex is sex: pleasurable for both genders, and potentially emotive and heart-breaking for both genders.

9. Women don't enjoy being raped. Slightly obvious one, but being raped is deeply traumatic and terrifying. There's a massive difference- and I could do a whole essay on this- between a woman enjoying being passive and desired in the bedroom because she's been taught it's disgusting and shameful to want sex- and a woman wanted you to violently assault her when she doesn't want to have sex with you. Idiot.

10. The vagina doesn't change shape permanently after sex. Even if her ex was massive. After about half an hour, it will revert to the original size. So unless she broke up with her phallic god 15 minutes ago, it's absolutely not something your'e thinking about. Her reaction might be different if she's used to a totally different man in bed: but isn't that a good thing? Wouldn't you want to have a unique relationship and experience with your partner? If you're seriously anxious about it see a therapist. But you're winding yourself up over nothing. I've never met any woman who left her partner over his penis. Personality, definitely.