Tracking your BBT....

I've been using Glow for two months and I'm TTC. No luck yet, so I decided I was gonna track my bbt. How exactly does that need to be tracked? I know it has to be first thing in the morning before I get out of bed. But what I mean is, does it have to be taken orally? Or can I use an ear thermometer as well? My oral thermometer doesn't work too well so I don't know if I can trust it...