usually I take my BBT first thing in the morning before I get off bed. when my alarm goes off, i grab the basal thermometer and take my temperature right away. that's the best.
The nurse told me BBT not working at all. The best is OPK and body mucus. I kept my BBT for 4 months now and I can compare it, but it's doesn't help me at all.
good luck
You need to use a basal thermometer and the only time it is taken is immediately upon waking. Before getting out of bed or moving around. fertilityfriend.com is a great resource for beginning.
When I charted my temps several years ago, I was told to do it FIRST thing in the morning - don't even get out of bed - take the temp in the bed.
Again, that was seriously 4 yrs ago, so things might have changed by now.
Good Luck!