Do I have to wake up every day at the same time in order to take my temperature?

No, although you should try to be as consistent as possible. In general, waking temperatures tend to creep up about two-tenths of a degree for every extra hour you sleep in. Thus, if you take it substantially later than usual, it may result in a reading that is outside the range of your usual pattern. If you wake up earlier than usual, you should take your temperature upon awakening, so long as you have had at least 3 hours of consecutive sleep.

Regardless, an occasional aberrant temperature can easily be dealt with by following the Rule of Thumb. You should also be aware that if taking your temperature feels like a burden, you can in fact take it for only about a third of the cycle without sacrificing contraceptive efficacy, as described in Chapter 10 of Taking Charge of Your Fertility.


How can temperatures be relied upon if I sometimes get a fever?

There may be several factors, from fever to alcohol to lack of sleep, that could affect your waking temperature. Yet this doesn't compromise your ability to rely on them while charting, because you ultimately want to identify a pattern of low and high temperatures, rather than focusing on individual ones. Outlying temperatures can be effectively dealt with by using the Rule of Thumb, which usually allows you to ignore them in interpreting your chart. In addition, you will always be able to rely on your other two signs to cross-check your fertility in situations such as these.
  

What does it mean if I don't see a thermal shift but I have very regular, 28-day cycles?

It can mean one of several things: First, you may be ovulating, but you may be one of the few women whose temperatures do not reflect the heat-inducing progesterone produced following ovulation. Second, you may indeed be having a thermal shift, but are not drawing the coverline correctly in order to accurately interpret your charts Third, and finally, you may not be ovulating altogether, although this is not that likely, since women with extremely regular cycles usually do ovulate.


Is it worth checking my cervical position?

Although it is not necessary to check your cervix in order to practice FAM effectively, I urge you to learn how to do so. At a minimum, I think you should practice checking in the days leading up to and just past ovulation, for the first few cycles that you're learning the method. Once you recognize how your cervical position reflects your fertility, you will always be able to use it as a cross check whenever you find the slightest ambiguity in your other two fertility signs.

The bottom line is that complete familiarity with the changes in your cervix will greatly increase the confidence with which you observe your fertility and overall gynecological health. And since it only takes seconds a day to check, my attitude is that for those few relevant days per cycle, you should just do it!

A distinct but closely related question is whether those women using FAM for contracption should ever check their cervical fluid at the cervical tip. The short answer is that it isn't necessary to do so, although if you want to be even more conservative than the FAM rules require, or if you simply want to know your cervical fluid status ahead of time, it certainly couldn't hurt (Remember that the cervical fluid you normally check at the vaginal opening might have taken several hours to trickle down from the cervical tip). Finally, checking this way may provide some couples with more time for unprotected sex.