CBADFM peak 3 days before AF???

I'm on my 3rd month using the monitor, the first month I had 20 highs, no lows or peaks. Did some research and found this was pretty normal. Second month I had 2 lows 6 highs and then 2 peaks followed by a high. However this month I have had 17 highs before I got the 2 peaks and a final high. This was on CD 27 and 28 (high on day 29) my cycles are regular always 29-32 days so my question is how have I got a peak so late in my cycle when AF iS due to arrive in the next couple of days?
Thanks, katie