Probable dates of conception would be july 15-17.

Ovulation typically occurs 14 days before your period starts.
Also have a read of the stickies in the pregnancy forum (the one called "read first" and scroll down to the "science bit").

How old are you?
Are you with the father?
Was this a planned pregnancy?

If you ask your doctor he/she can probably give you a better estimated guess than anyone here. If you got your due date by an early ultrasound then they can probably give you a better conception date then just going by your last period. For example, if I go by my last period my due date would be june 2nd and the conception date would be right around september 8th but by ultrasound it showed my due date being june 11th so the conception date would be right around september 15th. Looking back at my ttc journal I seen that the second conception date was more accurate due to the dates we had sex.

Same thing happened with my son. They went by my last period and set my due date at april 15th but then after an ultrasound changed it to april 28th. The conception date didn't add up with the due date of april 15th so I was happy to know that the date was wrong.

My whole point is, is to ask your doctor.