Hi, just started period 2 days ago, all of the sudden I get a 100 degree temperature, sore throat, muscle aches, cough, and here's the gross part, so sorry, my menstrual blood is much much darker than normal, like dark brown, sorry for the information but its worrying me, I usually use tampons, and did for the first two days but am now using pads because the color is worrying me. It is very abnormal for me to get sick, let alone run a fever... the last time I ran a fever I was 10 years old. Oh and I'm 20 years old and female if that wasn't evident. Also having a headache that comes and goes, the time of the month is never like this, I usually have the lightest and easiest period ever... if anyone can let me know if this could be serious that would be very helpful. Thanks.

A few things may be going on:
Is it possible that you have an old tampon (or part of one) still inside of you? If so, go to the emergency room and have it removed--you may be experiencing Toxic Shock Sydrome.
That is the worst case scenario. If I were treating you, I would assume that you have the flu. Sometimes menstrual blood will change when you are ill--become heavier or darker, for example. Illness is a lot like stress as it can change the way your cycle behaves in a particular month. This is your body's way of coping with the current situation.
Drink a lot of fluids, get your rest, try to relax. If your fever increases, check in with your doctor.
Best wishes!