I already had my period march 7 th 2014. now march 19 th i started brown spotting. mild cramping , what could be going on?

Breakthrough: This sounds like a hormone imbalance or breakthrough bleeding. Sometimes this occurs because estrogen and Progesterone (your 2 female hormones produced in ovary) are not in the right balance to each other. Sometimes it's due to pituitary or thyroid issues. And lasly, sometimes due to weight (too thin/heavy). If bothers you can consider birth control pills to help regulate. Best of luck.