29 day cycles, then changed

Pam
41yo. Mireya for 5 years, normal cycles before, normal after. Taken out Jan 2015; cycles back to 29 days from Feb-June. 
July cycle 25 days
Took First Response opk in June. Got low readings for a few days, then an indicator of ovulation on CD 17. 
So, I wanted to try opk again this month, but start it earlier since the cycle was not as it has been for the last few months. I began taking ClearBlue Digital opk on CD 6. Today is CD 8 and I went from Low to Peak today. Had sex in CD 6 and today. Today used Soft Cup after sex.
Is there a chance that my LH is surging because I'm older rather than as an indicator of ovulation?