@Sugar, moodiness sucks. Hormones are a bitch. It turns into demons during some months!

My poor hubby - he doesn't know whether he is coming or going. Poor thing!
Anyway, Ovulation predictor kits you use about four days before expected ovulation. If you have a 28 day cycle, then ovulation is approximately on day 14, then you start using the OPK's on day 11. You can use it morning and night until you get a positive result. My cycle is 27 days long, and therefore I start testing on CD 10, which is today. During the first two days, I only test in the morning, thereafter, I test morning and night...
EWCM is quite prominent during ovulation and the few days leading up to Ovulation. Some ladies have also reported getting it after ovulation. It is a great predictor of impeding ovulation, so it is a good way to estimate when to BD! I am! on CD 10, as already mentioned, and I have tons of creamy CM, not EWCM yet. The moment I see EWCM, that's when I know ovulation is almost due!
Hope it helps!