Brown discharge around time of period?

okay so a little less than a month ago i had unprotecte ANAL sex and as far as i know nothing leaked. i know theres a very small chance of getting pregnant fom that but that small chance freaks me out. anyway my period is due in the next 2 to 3 todays and i jsut found some thickish brown/red discharge. i had cramps yesterday and today too & hunger which i get usually during my period. i've never had this discharge before and i'm scared because of the small chance of pregnancy. is this just my period starting?