A week of spotting before period

I am 25 years old and my husband and I have been trying to conceive for several months now.  I have always had somewhat irregular periods (for the past 10 cycles my period has started on day: 21, 46, 23, 19, 25, 25, 22, 26, 23, 26).  Since we have started trying to conceive, I have several days of spotting (like 4-6 days) before my period actually starts.  I am little worried about the spotting because I never had spotting before we started trying to get pregnant - or at least not more than a day of spotting. The spotting usually starts off a brownish color and then gets darker  and redder right before my period starts.  I am worried this might be a sign of possible complications with getting pregnant.  Does anyone know what might be causing the spotting or if I need to see a doctor about this?  Could it be a sign of a luteal phase defect?