Hello everyone!

I've been having a little trouble lately and hoped you guys could give me some advice. So i am 4 days late, I have very little cramping, and have slight dark brown discharge here and there very light. I know dark brown is old blood, I am worried it may be implanting bleeding. I have been feeling so sore lately I'm not sure if it may just be stress, since I just started my last semester of college. Me and my boyfriend are pretty careful and always use a condom, but I know that sometimes they aren't reliable. Has anyone experienced the same thing? If I don't get my period by next week I am going to make an appointment.