Suggest Tests To Confirm Exact Date Of Conception

I want to know when i conceived. My lmp was on June 21, 2014. I had unprotected sex June 30 July 4 and July 11. My boyfriend said he accidently ejaculated in me on the 30th and 11th but not the 4th. But my doctor says i conceived on the 4th or 5th. My due date is March 28, 2015. Help?