What Causes Spotting Before A Week Of Menstruation?

We have been ttc since April and just this last month one week before my period on what should have been the 15th I had spotting which is something that I have never in my life had before. A mix of cervical fluid with a little blood in it. Hoping for a baby I was very excited! The 15th came and nothing, then the 16th nothing, then the 17th I had a normal period. One week after my period I again have had spotting two times. Is something wrong?! Am I possibly pregnant? What should I do?