BBT

Last month I used OPKs, but this cycle I want to use them and chart my BBT, I have a couple questions about it though cause I've read different things. First of all, do you have to use a BBT thermometer? They didn't have any at the Walmart here, just the Relion Digital 9 second readout one, so I bought that. Will it work or does it really have to be a BBT thermometer. Also, when do you start taking your temp, I am currently on CD 3 of a 27 day cycle. And when charting with a BBT, do you find out before your ovulating or after. I have read that you can only find out after cause your temp rises after you ovulate and I have read that you can find out before, cause your temp dips right before you ovulate, so I am really confused.

To correctly chart, you really have to have 3 months of charting before you know your cycle. You won't know before you ovulate, you'll only know after. I don't chart...I use the checking CM method. its the easiest in my opinion! That's how I got preggers again after 11 months of trying.  

So should I not even bother considering I don't even have the right thermometer?