No peak in 3 cycles

I miscarried 3 months ago and have been using the same ovulation sticks as before I was pregnant. For the past 3 cycles I have had since the miscarriage, I have had days of "high" results and no "peak"s, then "low". This latest cycle I've had other indications I may be ovulating soon after days of "high", but the results say "low" now without a peak. Why is this?