Our experience with Creighton was abysmal. The problem with Creighton is that it relies exclusively on one symptom, the cervical mucus, putting all of your eggs in one basket so to speak. Furthermore, without any cross check, it is difficult to know if the woman has actually ovulated, so the couple is constantly charting and constantly concerned throughout the cycle.
My wife could not make heads or tails of her symptoms and our professionally trained instructor was of little help. She did NOT want us looking for other symptoms and wanted us to try harder to interpret the mucus. Two unplanned pregnancies later, we were through with Creighton.
Overall, Creighton seems to be best for achieving pregnancy and perhaps for diagnosing irregularities, but IMHO it is not the best for TTA. On the other hand, some people love it. YMMV.
No experience with Billings, but it seems like a simpler version of Creighton. (Or more accurately, Creighton is an OCD version of Billings.)
The Couple-to-Couple League teaches sympto-thermal method, which tracks all symptoms. This gives more information, but our experience is that the information is not well presented and the teaching quality varies widely. CCLI seems more interested in teaching theology than biology. Some instructors are poorly trained while other do not take couples’ struggles with TTA seriously, saying “maybe God wants you to have another baby” or “abstinence can be a blessing in your marriage” when a couple has trouble avoiding.
Toni Weschler’s Taking Care of Your Fertility is THE definitive book on the subject. (Over 400 5-star ratings on Amazon.) She is not Catholic, but you can easily ignore the parts that are contrary to Church teaching. (She allows the use of condoms during the fertile period, but recommends abstinence due to the failure rate of condoms.) The presentation is simple and straightforward. Her book also comes with software and you can sign up to track your cycles online. After reading Weschler’s book, my wife FINALLY understood what was going on.
A lot of people have said good things about the Marquette Model. The Marquette Model uses cervical mucus to determine the start of fertility, then a ClearBlue Fertility monitor to confirm it. This seems to be simple and accurate. The only downside is the initial cost of the monitor and the $10/month for the test strips.
Another option that is rarely presented is the Ovacue fertility monitor. The Ovacue is a fertility monitor with three components: An oral monitor, a vaginal monitor, and built in fertility software. The oral monitor determines the start of the fertile window, the vaginal monitor confirms ovulation and the end of the fertile window, and the software puts all the relevant information together to tell you when you are or are not fertile. Preliminary results are promising, but there has been no major study on the effectiveness of this to avoid pregnancy. Additionally, the Ovacue is not cheap, although unlike the ClearBlue, there is no need to buy additional test strips.
Creighton Method:
creightonmodel.com/
Billings Ovulation Method:
boma-usa.org/
Couple to Couple League:
ccli.org/
NFP and More:
nfpandmore.org/
Taking Charge of Your Fertility:
tcoyf.com/
Marquette NFP:
nfp.marquette.edu/
Ovacue:
ovacue.com/fertility-monitors-and-nfp