Quoting Krystal M Guzman:" Its 14 days from your first menstrual day. but its not always 14 days mine was cycle day 17 to 19 I had ... [snip!] ... I had positive opk's. I have been trying to pg for the past 2 years but nothing so I think we just havnt been timing it right"Ok. The reason I'm asking is cuz when I used to ovulate (my period lasts 4 days) I would always get the O pains and positive opk 14 days after my period finished. So I could possibly be getting it around CD 18. And I always counted on the calender from that day 14 days for my period to start again and it always started on time. Now I don't know what the hell because I don't get positive opks anymore. I sure hope this next cycle has better results. I'm not messing with the Answer brand opks anymore. I don't care for the whole dip the strip thing. I'll just buy the epensive ones that have 20 in it that have the casing and everything. I bought the Walgreens brand last week with 7 in it for $18 and those things are a POS. I will never buy them from Walgreens again. I started exercising so hopefully it will help me kick start ovulation. My period is due to arrive around the 20th so we shall see.