Hello Sir/mam.. I'm Rishabh... N My Girlfriend Had Periods On

Hello Sir/mam.. I'm Rishabh... N my girlfriend had periods on 27th September.... N we had unprotected sex in october... But she didn't had her periods on time... We tried a home pregnancy test kit.. Bt it came negative.... Later on 1st November in d morning she told me dat she had bleeding n called it periods because of its smell.. Bt I'm doubtful about tell dis...
So plz explain about this situation