Last month (July) I had a regular period and I had unprotected sex twice after my period ended. Now in this month (August) I had unprotected sex once. I thought I miss my regular period so I took a test and came out negative. Then a few days later I started but the first day was brown the whole day then the next day really really light bleeding afterwards I only lasted for 3 - 4 days (this isn't usual for me). Could I be pregnant?