A Day-By-Day Guide To Your Menstrual Cycle, From An OB/GYN

Let's face it, the menstrual cycle is complicated. The period itself may be easy enough to understand, but what's happening to your body every day in between?

Despite being told about a standard 28-day cycle, there's actually no such thing as a "normal" menstrual cycle—the timeline will vary from person to person. In fact, one study published in the npj Digital Medicine journal found that only 13% of women had a 28-day cycle1, most peoples' were either longer or shorter.

Tracking your personal menstrual cycle can help you prepare for an upcoming period, inform you of the best time to have sex in order to conceive, and keep you in tune with your hormones. It is measured from the first day of one period to the first day of the following period and split into three different phases. Here's what's happening to your hormones during each phase.

Day 1: This is the day of your first bleed (more than just spotting), aka the first day of your period. Unless you're pregnant, hormone levels plummet and the blood and tissues lining the uterus break down and shed.

Day 2: The period continues. The second day of your cycle is generally a heavy one. And while your PMS symptoms have (probably) cleared, you might have some cramps that accompany the bleeding. This may be a day for super tampons that you'll have to change regularly. If you find a small clot in your pad, don't panic. That's perfectly normal for this point in your cycle. But if you're going through a box of tampons in a day and passing plum-size clots, get checked out by a doctor.

Day 3: This is often the final "heavy" day of bleeding. You'll probably continue to see red blood. You may also experience some changes in your vaginal pH around now, which could lead to yeast infections and bad odors. If so, try an over-the-counter vaginal probiotic to balance things out.

Day 4: Your period usually starts to lighten up, and may change in color from bright red to brown.

Day 5: If you generally have a five-day period, a panty liner will usually do it.

Day 6: For many, this is the first day you'll be free from a period. Others have periods that last up to seven days, though, which is perfectly normal.

Day 7: By now, your period should be completely or almost gone. This means that your body is gearing up for next month. Small follicles (little cysts on the ovaries that will release an egg or two) are starting to form. Estrogen levels are starting to rise, testosterone is still low, and progesterone is still absent.

Day 8: Those follicles are growing and preparing to release an egg. As the eggs start to develop, they produce estrogen, so estrogen levels will start to rise. Testosterone and progesterone levels will stay the same.

Day 9: Over the next few days, one follicle will continue to develop toward reaching maturity. That extra estrogen causes the lining of the uterus, rich with blood and nutrients, to thicken, so it's ready if a fertilized egg implants.

Day 10: Estrogen production should now be off the charts. And your endometrium, or the lining of the womb, continues its plans to house a potential pregnancy.

Day 11: If you're trying to conceive, now's the time to kick your efforts into high gear since you're either ovulating or getting close to ovulation. If you're not always in the mood, now would be a great time to introduce a lubricant to your routine, to make planned sex more enjoyable. Be sure to choose a fertility-friendly one for best sperm motility, like Pre-Seed2. Other lubes can harm sperm.

Day 12: Even though you may not be ovulating yet, your fertility levels are high due to increased estrogen production—and because sperm can survive a few days in the woman's body. Your cervical mucus is flowing and stretchy, and the main follicle should be fully ready to release an egg while the others shrivel up. You may notice increased libido around this time as testosterone (the main libido hormone!) levels are surging. This is nature's way of encouraging sex at peak baby-making time.

Day 13: Estrogen levels are peaking, and your body is about ready for the egg to emerge from the ovarian follicle (aka ovulation).

Day 14: You're ovulating! The egg is released from the follicle. You may feel a twinge of pain or have a little spotting, which is perfectly normal. This is your best baby-making day, so if you're trying, whip out the lube and get to it. If you're not, don't skip that condom.

Day 15: Your egg is starting its journey down the tube in hopes of a sperm rendezvous. If you don't want that to happen but had a condom mishap, it's not too late to take emergency contraception.

If you are trying to get pregnant, intercourse on the day after ovulation (just in case) is good practice. If things start to get funky down there (a common occurrence with frequent intercourse), reach for pH-balancing gel to keep your vaginal pH in check. Now your estrogen and testosterone levels are starting to drop, while progesterone levels are rising rapidly.

Day 16: The egg, ever hopeful, is still hanging out in the tube waiting for Prince Sperm.

Day 17: The lining of the uterus is getting thick. If the egg has successfully united with sperm, it will soon make its home there. If conception hasn't taken place within 24 hours of ovulation, the egg will die. Estrogen levels are on the way down, while progesterone levels are sky-high.

Day 18: Now estrogen will start to make its comeback. Progesterone levels are still up there.

Day 19: If you're trying to get pregnant, or concerned that you might accidentally be pregnant, don't head to the drugstore yet. It's still too soon to take a pregnancy test.

Day 20: The end of your cycle is nearing, and it's around this time that PMS symptoms will start to rear their ugly head. You may feel slightly bloated and moody.

Day 21: If you're trying to get pregnant and want to confirm that you've ovulated, this is the perfect time for your doctor to check to see if your progesterone is elevated.

Day 22: Time to check your tampon stash so you won't have to make a midnight trip in a few days.

Day 23: PMS is in full swing. Treat yourself to a bubble bath or a nice bar of chocolate.

Day 24: About a week after ovulation, your progesterone levels will be at a high. Estrogen will start to drift down.

Day 25: This will probably be your worst PMS day. Expect major bloat. And don't be surprised if running out of ketchup brings on unexpected weeping.

Day 26: Don't, I repeat, don't get on the scale. It's not you; it's that premenstrual fluid retention.

Day 27: Get excited: PMS symptoms are winding down.

Day 28: This is about the time that your cycle comes to an end. If you're not pregnant, your period is on its way. The uterine lining is at its thickest to get ready to shed. Tomorrow, the cycle starts again.