Hi. I always have this issue where my period comes for 15 days every month without fail. My period is regular and I have not missed it every month ever since my first period when I was 14. It will usually heavy on the first 3 days and subsequently it will be more like a dark brown phlegm. My question is when is my ovulation day? I have tried to buy a test kit to check my ovulation period but it has always been negative. I am also experiencing pain during intercourse. I have bought lubricant but it was not helpful.

Please advise me on this matter. Thank you very much in advance.