How accurate is dating done early in pregnancy?

Sh
Being single and "having fun" are all well and good... Till you get a bfp! I'm pregnant and wondering if I can be spared the judgement and embarrassment of paternity issues after my baby is born. Logic would say the gentleman I had unprotected sex with during my fertile window is the father instead of the partner who used a condom after the fertile window... Sigh I can't be mad at anyone but myself.