Amy Schumer said in her HBO special that one of her New Years resolutions was to “just once take off a pair of underwear and make it not look like I blew my nose in it.” But guess what: Vaginal discharge is totally normal.

What you might not have realized is that your discharge actually shape-shifts throughout the month, too. And it turns out, the secretions produced by your vaginal and cervical glands can offer big clues into your health, says gynecologist Sherry A. Ross, M.D., author of  She-ology.

Among them: where you are in your cycle and, if you’re trying to get pregnant, when the best time is to get busy.

Changes in consistency can either help move his swimmers through to the uterus, or straight up cock-block them.

The average woman produces about a teaspoon of discharge a day, but “there is no 'normal' amount of mucous versus too much or too little,” says Sheeva Talebian, M.D., a gynecologist at the Colorado Center for Reproductive Medicine in New York City.

But based on your own normal, you can decode your discharge with the calendar below.

Learn how to keep your vagina happy and healthy:

Days 1 to 5: During your period there’s very little discharge at all. You might still notice a bit mixed in with your blood, but it should be light, says Talebian.

Days 6 to 8: As estrogen levels in your body drop, secretions become thick, white, and clumpy.

You may also notice dark brown spots for a day or two—don’t stress; it’s just old blood from your period.

If you're trying to get preggers, this is no-go time; that sticky secretion blocks sperm.

But if you're not trying to get knocked up, you should still use protection to be safe, and also to avoid STIs, says Talebian.

Days 9 to 12: As the body ramps up for ovulation and estrogen levels rise, the fluid becomes creamy like lotion, and there will be more of it, compared to post-ovulation, says Talebian.

While these aren’t ideal conditions for baby-making, sperm can reach the uterus. An egg might not be around yet, but his swimmers can live there for up to five days, waiting.

Days 13 to 14: Ovulation! Your mucus will be similar to egg whites—clear, slippery, wet, and stretchy—to help his sperm travel up to the egg, says Talebian.

That’s why the pros call it “fertile mucus.” Want to stay child-free? Put a lifeguard on duty (be vigilant with protection).

Ready to get preggers? It's go time.

Days 15 to 28: As progesterone levels rise, your fluid becomes thicker again, and gradually disappears. Sperm can't swim in these conditions.

So keep an eye on what's going on down there, and remember, any of the above changes are totally normal.

But if you notice something unusual—like if your secretions become yellow or green in color, take on a cottage cheese-like consistency, or smell foul—call your M.D.

Ditto if you notice pain or itching. You might have an infection, like pelvic inflammatory disease, or a yeast infection.