what could it be?

i had protected sex today and started bleeding during sex, i thought i started my period so we stopped but there was definitely blood on the condom. it didnt turn out to be my period because i didnt leak later on during the day and there is no indication of a period. i had unprotected sex exactly last week but ended up using a condom towards the last few moments of sex incase my partner was on the verge of finishing. im expecting my period in 6 days. why did i bleed during sex? was i spotting? if so why are the reasons im spotting? i dont often have irregular periods. im just curious