Why Am I Having Light Period From Past Two Months?

My period usually comes on the 7th of every month and up until december I had normal bleeding and a normal period. On January 7th 2010 I had light spotting that lasted only about a day.It happened last month too. This month on the seventh I was spotting and have been until this morning when I woke up and I went to the restroom and it was done. I took a pregnancy test and it came up negative. Is what's going on normal or not? I need to know what's wrong with me.