Yes, definitely this. There is a “monitor-only” version of the method, but I can’t say I’d be comfortable relying on it. On a couple of occasions I’ve known the monitor was wrong because I was cross checking. I’ll add though that the monitor was wrong very likely because I was wrong- sometimes you’re a little bleary eyed in the morning and don’t hit the stick properly…or sometimes you just get a faulty stick and you can tell because of the way it looks. In that case I just assume it’s high and wait until the next day, and will use an OPK if I think it’s close enough.
It’s important to remember that the Clearblue monitor is designed to help women become pregnant, not the other way around. It works well to avoid, but the method itself has to be followed very carefully (for instance, just because it says “low” doesn’t mean it’s a non-fertile day).
We used it for two years and have found the method very reliable. It’s easy to learn and is especially useful for women who have a hard time with temps. I had tried STM previously and it just didn’t work for me.
The monitor itself is a little pricey. The sticks come in a box of 30 for about $35 on Amazon, and they typically last me about three months unless I have a weird cycle. Also, once the monitor reads “peak” it will ask for a test for a few more days but you don’t need to bother since it will always read “peak, peak, high, low”- saves sticks.
All in all, I really do like the added security the monitor gives me. Like anyone who uses NFP, you get pretty skilled at figuring out CM patterns, but the peace of mind when I look at the monitor and know I’m still doing it right makes me feel better.