I got my periods one week early and it goes in 3 day.any reason?

It is normal for a women to get there period early, but if you are saying it only lasted 3 days, if there is a possibility you are pregnant I recommend taking a pregnancy test. Now if it just came early and lasted a week, then it should be fine since sometimes that your period comes early do to medicines, or sometimes having a clean system, losing or gaining weight is another factor.