When did I conceive? Who is the father?

Patient: Hello! My last period started July 23rd 2015. I took a pregnancy test, Sep 2/15 and it came back positive. I have a possibility of two fathers and I hoping to narrow it down. One guy I had sex with on Aug 5 and 8th we were unprotected but he never came inside. The other was the 11th and he came inside. All calculators online are saying I would of ovulated around the 6th. Do you have a better idea who it could be?