cikao,
Yes, it is quite difficult to check ovulation if your M cycle is irregular and it is unusual to have 15-day of period?? I don't know your age and how long you have been tried to have a baby. I suggest you to see 婦科醫生 first to have a hormone check up on Day-2 (抽血) On the other hand, you can see 中醫調理身體, 我懷疑你可能身子太虛....