What Causes Stomach Cramps And Brown Spotting Before Periods?

For the past few weeks I have been having cramping everyday and back pains (lower back pains mainly).Today I've experience brown spotting and a minor headache. Usually I have the same symptoms before my period but when I get brown spotting my period comes right after usually the same day. This time my period has not started and my stomach still feels weird( on and off cramps and bloating).