I'm assuming you are asking because you slept with more than one guy in the same month. If you were not charting your cycle, there would be no way for anyone to know when you ovulated. If your cycles are irregular, even less of a chance of knowing.
You may need to get a blood test when the baby is born.
I am a worried mother - I received a call from a young lady stating that she is due on feb 11th and it is my 17 yr old sons child. There are alot of odd things surrounding the conversations. I spoke to my son and he told me that they did have protected sex the 2nd weekend of June. From my calculations she would have conceived the baby around may 20th. Is that correct? How much time on either side of the conceived date can you go either way???