Most women know the basics of their cycle. It's typically 28-30 days, you ovulate in about the middle of that and if you're pregnant, menses stops. But that's a very, very basic understanding. Did you know that your cycle actually has four parts? Did you know that your body temperature changes to reflect that? And did you know that that fluid that seems to change so much is also a reflection of that? Did you know that your cervix changes? Even your saliva changes!
First, we have menses. That's your period. It lasts 2-5 days in the average woman and your cycle starts on the first day that you bleed--not the first day that you spot. That's Cycle Day 1 or CD1.
On CD 1, your temperature will be a little above its lowest and cervical fluid (also known as cervical mucus or CM, but fluid sounds better, doesn't it?) will be obviously hard to determine. Your cervix will be hard, like the tip of a nose, high up in your body and closed.
The next phase of your cycle is called the follicular phase. That's when your follicles are maturing and growing eggs to be released in the next phase. You grow 5-7 eggs and release FSH (Follicle Stimulating Hormone) that causes the follicles to mature your eggs. They start producing estrogen that, when it peaks, stimulates the release of LH (Luteinizing Hormone) that is detectable by ovulation predictor kits (OPKs). The reason that they require a dark line to be positive is because when the LH peaks, that's when you release your egg(s). The LH surge (the highest concentration of LH) occurs 12-24 hours prior to ovulation but LH begins to rise about 36 hours before ovulation. Your temperature may go up and down a little, but it will stay in the same vicinity during these two weeks (approx).
Next is ovulation. In a woman with a textbook cycle, this happens on CD 14. This happens when the biggest, most mature egg is released at the peak of your FSH release. Sometimes two or even three mature enough to release. This is what causes fraternal multiples. The rest of the follicles and developing eggs die around CD7 or so.
Just before and during ovulation, your fluid will become watery or like the consistency of egg whites. That's fertile fluid and yes, the most fertile is called EWCM (egg white cervical mucus). It gives sperm the ideal environment to reach the egg (and facilitates sex). Your cervix moves down and opens, becoming soft, like lips. Your temperature may plummet or it may not move at all.
Sperm can live up to five days in a woman's body, so if you have unprotected sex as close as that, you have a chance at having a baby--and probably a girl. It's not very likely, though--sperm rarely lives more than three days and it depends on how 'hospitable' your body is to it.
The final phase is called the luteal phase. The corpus luteum is the dominant follicle, that is transformed by LH and starts producing progesterone. The day after you ovulate, your temperature jumps. In the space of three days, it can rise as much as a whole degree.
Now, all of this temperature stuff can only be monitored first thing in the morning. Basically, you set an alarm that lets you have had at least 3 hours of uninterrupted sleep (mine's set for 9:30am, but I woke up every day for the last two weeks at 8-something and temped--it's important to temp when you first wake up, before you do anything else, to be the most accurate) and take your temp. Write it down or memorize it (or use a thermometer that remembers) and go back to sleep or get up for the day.
The luteal phase ideally lasts 14 days (the 'two week wait' is what it's referred to by women waiting to see if they are pregnant for any reason). Few things are ideal, however, and it can last 12-16 days and be perfectly healthy. 10 days is considered the minimum length of a LP to last and still be able to become pregnant. Now, it ends on the day your period starts, so that's why it's important to last long enough for a baby to implant. I had a 7 day LP and still managed to get pregnant, but I lost the baby. A LP that short is defective. My first baby was conceived with a 10 day LP (approx, as I wasn't temping).
The luteal phase is largely the reason for variations in cycle. If you ovulate on CD 16, you might have a 30 day cycle. If you ovulate on CD 12, you might have a 26 day cycle, so on and so forth.
The cervix closes and rises back up into the body at this point. It becomes firm again and fluid can vary from this point and doesn't matter much. You can start producing 'fertile' looking fluid as your menses approaches or when you become pregnant.
If you are not pregnant, the corpus luteum dies, your temperature drops and within a day or so, you begin menses.
If you are pregnant, your temperature stays up (but can fall after a couple weeks, so it's important to stop temping so you don't become frightened if it drops--it becomes useless after you're already confirmed pregnant).
You can read more about the phases of your cycle here if you like or in the book Taking Charge Of Your Fertility, which is the highest rated book for learning about how your fertility works. I prefer Fertility Friend myself, as it's basically the Cliff's Notes version, but I haven't read TCOYF to say for sure. You can sign up for an account to track your cycle at Fertility Friend, too!
If you want to chart your temperatures, it's important to use a BBT thermometer (I do not recommend Walgreens Brand--while I have successfully used it to chart for the last two months, it is horribly inaccurate in that it seems to have preset temperatures that it is unable to vary from.. my old one from Wal-Mart was slow and the kids lost it, but it worked much better... most drug stores carry them) as it measures to the hundredth of a degree and not just a tenth. Speaking from experience, yes, this matters.
An interesting thing about pregnancy tests and ovulation predictor kits (or ovulation tests) is that the hormones they detect are similar. You can use an OPK to detect pregnancy! The POAS lady describes it this way: Think of them as identical twins, where hCG (human chorionic gonadotrophin--or pregnancy hormone) is wearing a hat. Now, an OPK can only look at the face of the twins, while the HPT (home pregnancy test) looks for a hat.
So, an HPT cannot see LH (what the OPK looks for) and can only see hCG, while the OPK detects both. Since hCG is only present in detectable levels during pregnancy, a line is a line on the test, no matter how faint, as long as it shows up in the test time. Anything after 10 minutes is an evaporation line (which can still show the pregnancy line, but if it wasn't there a minute before, it's not a positive test). With LH, it's a surge that triggers ovulation, so only a nice, dark, clear line counts.
This is one of my own charts (when I got pregnant with Naomi) to show you how temperature charting works (note the dip at CD7--that's an implantation dip; unconnected dots were artificially high temperatures from illness; the - test lines were confirming that my early loss pregnancy had passed):
So, I hope that you now have a better understanding of how your cycle (and your body) works!