what would you ladies think

Benjibellamommy
I had my son in June 
I didn't get my first period until sept 27 was not on any birth control had an accident with a condom o sept 15 we also had sex sept 21 & 25 but used the pull out method I know nothing got in since he pulls out a little before time my question is I had blood exam on the sept 27 as well saying negative does that mean the incident on the15 doesn't matter anymore since I got my period the27 ? 
Was only breastfeeding for 2 months as well