Late but protected sex?

Okay, so I'm kind of freaking out. I'm almost a week late. I'm usually Very irregular anyways. I've had sex twice but all protected, nothing broke. I've been drinking more alcohol than usual and have been transitioning to starting a Masters program and moving to a new state. Last night when I went to the bathroom there was a small amount of bright red blood in my undies, but when I wiped, there was brown on it. I'm freaking out, can someone please explain? Thanks so much!