Cycle day 25.....of 28-29.....16 days of high.....no peak

I have been using the CBFM for the past three months to determine when exactly I ovulate. Month 1...started testing on day 9 got L....day 10 11 12 got H...day 13 and 14 P, Month 2...started testing day 8 got L....day 9 and 10 L...day 11 and 12 got H, day 13 and 14 P....this month day 9 and 10 got L....11-25....H....currently on cycle day 25....of a 28-29 day cycle.....what the heck is going on? as my blood results from the doctor show ovulation on day 13...is my monitor faulty?