TTC watching BBT and confused

[Salley]

I've been tracking my BBT since two days into my AF. Initially I was using a normal thermometer before I read about why a basal is important for that extra 10th of a degree. Every morning I pop the thermometer in my mouth and wait for the beep, half asleep. The readouts seem to be sporadic. My base is 97 but over three days I got 97.27, 97.57 and 97.29... is that .30 spike normal? This TTC business is daunting.. I'm trying everything I can to be successful. I still don't completely understand BBT... what kind of spike will I see when I ovulate? And when my temperature does spike doesn't that mean I already ovulated? So confused...