I have some questions regarding NFP. My husband and I began taking classes in using NFP (Creighton Method) about 2 years ago to try to space out and avoid another pregnancy. During that time I was still breastfeeding my second child. Reading my signs was not easy during that time period. I had pretty much constant sticky mucus. The instructor tried to teach us an alternate version with yellow stickers, but interpreting signs was extremely difficult and I was very nervous that I might not be able to tell if I was ovulating (since child #2 was conceived when I was still nursing child #1, before I had had my first postpartum period). Even when my cycles eventually returned, they were very irregular (varying as much as 21-35 days in a cycle), and double peaks were not uncommon. I had a hard time telling how sensations of mucous felt - smooth or lube. Our NFP instructor, while very nice, didn't give us much confidence or greater understanding of the method. Following the rules often only gave us an infertile window of maybe one or two days each month. As I have a low libido this was not as much of a struggle for me, but it did have a very negative effect on the unitive aspects of our marriage (which I won't discuss publicly on this forum).
I observed my signs daily and tried to follow the rules for infertile periods, but am now 6 months pregnant with our third child. I thought we had waited until phase 3, but as far as I could tell in retrospect I think I misread a yeast infection for an early peak. My husband had doubts about the effectiveness of NFP methods before we started NFP classes and quite honestly this pregnancy hasn't helped convince him that it can work for us - perhaps for people with regular cycles and sleep patterns. I will admit that I am more nervous and have more doubts about the effectiveness of NFP too, especially since I'm not sure I trust my interpretation of my signs anymore. On top of that there were times that I was lax at recording my signs on my chart. My husband rightfully scolded me for sloppy record keeping and I think he blames me for this pregnancy - with some justification, but I don't think it was charting error that made a difference (and I'm not just saying that to absolve myself from mistakes).
We are adapting to our unexpected (but loved) third child on the way, but both my husband and I feel pretty strongly that unless God has other plans for us that having a fourth or more children in the near future is not something that we want to deliberately try for in the near future (if in the future at all). We could probably adapt financially, but emotionally providing time and support for the two we already have seems insufficient already and somehow we will manage with a third, but I'm not sure it would be in the best interests of our current and future children for us to have additional children. My husband believes me that I would honestly intend to do better on charting in the future, but is convinced that despite good intentions I will probably be lax in my charting. I would like to prove him wrong, but I had intended to better in the past and failed to keep the promise so there is not much I can do or say to convince him. Even if I have perfect record keeping with my chart, how helpful is it if I can't interpret my fertility signs? - not very. Even though my faith in NFP has been reduced, I would still like to try to follow Church teaching with regard to NFP.
What should I do from here? Should I look into instruction into another method of NFP? Creighton seemed to be the most scientifically backed method which is a plus but perhaps learning more about Sympto-Thermo method with cross-checks would be good. On the other hand our Creighton instructor discouraged combining different NFP methods so I'm not sure. Also the "iffy" "maybe fertile" days with STM make me nervous. I want to be absolutely sure about my fertility signs. I would also consider using a fertility monitor as an added check to my charting and reading my signs, but am not sure which fertility monitor(s) would be best. I know Marquette method uses the Clear Blue Easy (which uses LH and estrogen levels I think), Others use BBT (like LadyComp), which I would need to track if I were using the STM method. I think OVaCue uses electrolyte levels. I had a hard time finding unbiased comparisons about use of these monitors (most of the information either comes from the manufacturer or just tells how it works but doesn't compare with other types). How do I convince my husband not to give up on NFP? Also I plan on breastfeeding baby #3 for at least a year and how can I be sure about fertility during extended breastfeeding this time around?