You seem to be having 35-40 day cycles according to the trend of the last 3 cycles. In such a case, your fertile days would be around day 21-26, but in a broader sense they may be taken as from day 15-day 30, to cover even shorter cycles. You can predict your ovulation time from the ovulation kit also. You can notice the spike in basal body temperature
if you record it, at ovulation. You may also notice profuse vaginal discharge
at the time of ovulation. Wish you good luck.