I Have Been Experiencing Light Bleeding Between Periods And Have

I have been experiencing light bleeding between periods and have become a little concerned. It started Monday Feb 22. I actually had my annual well woman on Tues 23rd and my doctor said that he could not find anything that looks to be causing the bleeding like polyps or anything. My Pap and bloodwork all came back normal. My doctor said it may be caused from a missed pill, but I only missed one and this has never happened when I have missed one before......But I am still bleeding, I am 35 and on birth control, and my regular time for my period should start Mon or Tues of next week. I am almost at 2 weeks of bleeding now and if I still bleed through my period could go to 3. Is there anything to be concerned with? Should I do anything?