High day on period

Hi I just had a very weird month and wondered if you could help explain it.

Last month was a pretty regular month for me, 28 day cycle, high from day 9, peak on 13.

But this month I didn't get a high day till day 16 of cycle, still getting high days till present - day 20, and now my period has arrived a week early, but still testing as high. Very confused and disappointed.