BBT Thermometers?

Bees

What brands do you ladies use? I've been using this one by Provèn but it feels really inconsistent to me. I'll take my temperature in the am and I get the same reading as the day before ex: 97.77, then I'll do another read thinking its weird to get the exact same number. Second read is 96.78. Then I do a third and its 97.56.

Curious what you lovely ladies use and love! Thank you!