Spotting, what does this mean?

My period ended February 4th. I have a pretty normal cycle. On the 13th I had a little bit of pink on my underwear then it stopped. On the fourteenth I had a little brown (old?) blood all day. Today the 15th same thing except there was a big clot. and now its back to being only a little. Am I getting my period super early? Could I be pregnant? I shouldn't get my period for another 10 or 11 days. I don't really have cramps or anything. My lower back kind of feels stiff. Anyone know what's up?