Not necessarily. Some women have a lighter period and still be pregnant. What you can do is one get a blood test to see if you are pregnant or wait about a week and a half and do a pregnancy test then. If you do it to soon you won't get a very good reading.
I got my period a week and a half ago and its not stopping I have never had a period last longer then 4 days. I did take plan B when I was on my period.