If that was a true period 8/5 your likely ovulation would be 8/19 and you could not be pregnant from sex this cycle just yet.
Is it possible you are pregnant from sex two weeks before that period and had an in-pregnancy bleed - lighter and shorter than normal period. You would likely have other early pregnancy signs if that were the case - fatigue, changes in breast, nip, appetite, peeing, head and backache etc. Run a home preg test to sort it out.