I need help

Ok guys last time I had sex was on the 28/07/18 ,our actions were cut short so there wasn’t a lot of time to get pregnant also he didn’t come inside me (I was ovulating on that day) about 12 days after it looked like my oeriod came it lasted 6 days and I filled a pad a day but usually my period is much heavier.Today it’s my period due date and at about 11 am I wiped and I saw some Red but it hasn’t got any heavier and only shows up when I wipe (it’s now 17:30 pm) .Can any of you give me your opinion,is it for sure I’m not pregnant and the flow will eventually get heavier or did it happen to someone else and there’s still a chance??