Please help! Need your input!?

Hey ladies! I'm new to this and hoping someone could explain something for me. I've always had a 5-6 day period always heavy the first two days and then lighter the rest, and also right around 30-32 days. This last period was almost a week earlier and only lasted 4 days and was not even heavy the first day then light (not using super + tampons like usual) to light (using regular tampons which I never use) the rest. And now (4 days later) I am having a light pink and brownish discharge when I'm supposed to be having my normal period (but I'm not because I already had it). Could this be implantation bleeding? I'm not sure because I read that implantation bleeding is supposed to be before or during your missed period. I'm confused on why my period happened like this only this month. I've also had terrible migraines as well as fatigue. Someone please help!