Ovulation question

My period is regular 26-29 days

I get spotting before my period (last 2 months I had 5 days of brown spotting before period)

Am I counting CD 1 wrong?? I count CD one when I get fresh red blood not brown spotting.

I’ve been tracking opk’s now and according to that I’ve ovulated on CD 16, CD 15, CD 14, now it’s looking like CD 12/13 this month?!? Why is it moving? What am I doing wrong haha