How would you based your ovulation days if you missed a period?

Well, you can't really and be positive on the accuracy of it. Sorry. If you are always like clock work, then it may be something else. You would be testing positive by now for sure if you were pregnant with the last ovulation. I was never like clockwork. Always had irregular periods and then about 4 years later I found out that i had polycystic ovaries. But, basically they told me if I miss a period then there;s no way of telling when ovulation occurs. I know when it happened because I'll have a period, but I don't know when its coming.... see a doc if possible.