Curious

Hey guys I’m just very curious trying not to jump to conclusions . But I am 3 days late on my period and today is the 4th day and when I wipe I see blood but not a lot of blood just light pink . The last time I had unprotected sex is the beginning of the month and we had sex right after my period like literally . Should I be worried ? Is this pregnancy or it’s just happens to some women from time to time ?