Opk question??

Amy • Married 5-20-12 to my love since `08 ❤️ Our 🌈 Lucas arrived 5/16 - baby #2 became an 👼🏼 in 9/19
This is my first month using OPKs. Glow says green week starts tomorrow. I've been using the OPks since my period ended, and they've all been pretty light. Then yesterday's was pretty dark, but I don't think I'd say equally as dark as the control line. Then today, super light, and my bbt dropped ( I forgot to take it yesterday, but since Friday its dropped from 97.51 to 97.35 today)
This is my first month using opks, and I was wondering if a fluctuation is normal?