I just keep track of my basal body temp and my cervical discharge (during ovulation you have a distinctive "egg white" type mucus) to determine roughly when I am ovulating. The number of days between ovulation and menstruation is the luteal phase, and it should ideally last 10-14 days. Less than 10 days usually signifies estrogen dominance and will make it very difficult to get pregnant (as the fertilized egg is unable to attach to the uterine lining before the period begins). So, that's how I keep track and I find it to be very easy and helpful. Hopefully I will start to see an improvement soon (my luteal phase was only 4 days).