What Causes Light Period Bleeding?

So I started my period last Tuesday 12/10/13. Its been light. I usually gave a heavy flow and it usually last about 5 days. Well Im still bleeding today makes day 9 and today when I wiped, its a brownish color and clear discharge. Ive been a migraine everyday this week. Me and my husband had unprotected sex on Monday 12/15 and 12/16What should this be? I am so worried. I dont have insurance to go to the doctor. Please help