Unprotected on the sixth day of my period?

My periods started on Oct 17th & on Oct 23rd i had unprotected . I stopped chumming on the 5th day but had on the 6th day thinkin i will chum but i did not. however he d outside me but i still have fear if it remains. Are there any chances of getting pregnent . Please advise. I have not taken any pills. Can some one give me a relaible answer.and i have a cycle of 28days, my periods are regular. Aslo when are the safest days to have . Please advise. And do we get pregnent in just one in which very less seprms must have gone inside. Because he d outside me. HELP