Best Basel body thermometer

Renèe💍married💛ttc #1 • 39, married, TTC #1, T1 diabetic

Tried using opk's for 6 months, no luck. Want to start temping but know nothing about it really, what is a good thermometer for starting? Are they available in stores or just online? Do they show when you will ovulate or just the fact that you DID ovulate? Should I use opk's as well? Thanks in advance for any insight.