Spotting between periods? (tubes tied)?

My monthly cycle ended approx 10 days ago, it was a normal, 6 day on time cycle. 4 separate and non consecutive days I have had issues with spotting, it will last maybe an hour and then nothing again. It has been like Tuesday, Thursday, Saturday and now today. I had my tubes tied 6 months ago after my 3rd C-section. Any idea what would be causing it?