BBT newbie

Em

Hey,

So after ttc for 2 months using only opk I decided to start tracking my bbt.

I just read that I should start from day one of my cycle but I will only start at day 3. Does it make a lot of difference?

Second question - I read that you can take the temp orally or vaginally. Are both accurate the same way? Will be much easier doing it orally since I know you need to do it first thing when you wake up.

Thanks a lot !