What Causes Vaginal Spotting Along With Stomach Cramps And Dizziness?

Hello I received my period on January 12 2015 for four days. I spotted a few days before my cycle maybe a week. After my period a week later when I wipe it s light pink only on the toilet paper then it will stop then continue like three days later then the next week it s light spotting again on on the tissue along with it I have mild cramping just for a little while I have been feeling light headed during the spotting what can be the problem