So last month I ovulated on CD24 (as confirmed by BBT) and I didn’t get my high OPK until CD23.

Well this month I’m already getting high OPK’s at CD11, so it looks to be I could be ovulating earlier (need to check my BBT)

My question is - is it normal for ovulation to change this much? Let’s say I ovulated on CD14, that would be 10 days earlier this month than last. Is this normal? My cycles do range from 30-35 days.