LH Surge & Ovulation

Morgan

So I’m pretty new to tracking my cycles as I just got my IUD removed 12/3. My first cycle tracking with OPKs and BBT, I ovulated likely on CD21. My OPK showed peak LH on CD 19. Currently I had 2 days of high OPK, with peak being yesterday on CD18. Is it normal for things to fluctuate this way with cycles, even slightly? Thanks!