About 2 weeks before my schedule period me and my boyfriend has unprotected sex. I am on birth control and have been almost 2 years, I take it regularly but there is days I miss. Well when it was time for my period it didn't come. 3 days later I started lightly bleeding & it was brown, some pink. Lightly I mean I could of went without changing a pad or tampon the whole time. It last 2 days. I didn't have any symptoms of my pms, no cramping or anything. Is there a way I could be pregnant? I know there is always a possibility but seriously. If so when should I take a test? Also I'm not under any stress & I always have regular periods that last 3-4 days. When should I take a test?