replied 4 Days.
Thanks for your query at DoctorSpring.
To answer your first question - sperm can survive inside the female genital tract for upto 5 days, sometimes even 7.
As you can see this complicates the picture, because counting from 5th June ( Man 1 ) to 8th June ( Man 2 ) - the difference is just 3 days, so the sperm fertilizing the egg could have come from either of them.
You must have had your period sometime in the end of May. That would make your fertile period to be more likely around the 8th, 9th and 10th of June.
Please provide the date of your last menstrual period, and the normal length of your menstrual cycles, so I could hazard a further guess.
Even otherwise, with all conventional methods, such as ultrasound, the expected date of delivery etc, it is impossible to pinpoint the father. This is because all these methods carry an error margin of plus or minus 7 days, and the gap between the two different men is only 3 days - too narrow a window.
The ONLY confirmatory test would be a DNA paternity test, the rest would fall in the realm of speculation - not advisable for such a serious issue.
Please feel free to discuss further.