Help please

Okay I’ve heard some people say they’ve had spotting up to a week before there expected period Nd was pregnant but I’m currently 4dpo I had intercourse on my highest day of ovulation Nd i spotted yesterday like out of nowhere I had minor back pain Nd like a little stomach twinge so i didn’t pay it any attention until I went to use the bathroom Nd there was like pink streaks only when I wiped 🤦🏾‍♀️this never happened what can it be ?