If you track your cycle with opks to let you know when your about to ovulate (take them 2 days after period 2 times a day between 11am and 8pm. Your lookin for both lines the same color or test line darker then control. Whatever comes first is your first positive. Ovulation is in 12-48 hours. If you add BBT to confirm ovulation you will know when you ovulated, dpo, luteal phase length (is from the day after ovulation to period which stays the same each cycle give or take 1-2 days. Average length is 12-14 days give or take 1-2 days.) when period is coming by temp drop or if you miss your period and your temp stays up then there is a chance for pregnancy