Could I be pregnant? I have listed a few more details listed below... Please help?

Ok my period starts they same time every month. Last month I started on time abd it was a heavy period about two days into it I found out I had the swine flu & my period lasted about 3 days longer than normal. Then throughout the month I had a really dark spotting it wasn't enough to wear a tampoon but enough to need a pad off & on for most of the month. Now it's time for my period again and it started on time abd was heavy to normal for a day or so & mow it's like nothing. I have no other symptoms. Should I be worried? I tend to over react about these kinda things. Oh btw I do take birth control. Any ideas???