Irregular periods?

Normally my period comes regularly, maybe a day or two late. The last 2 months it has come nearly a week early, which is unusual for me but obviously not a problem. Today I started my period again, and it is just over a week since my last period. Is this something to be worried about? And has anyone experienced this before? From a slightly stressed 18 y/o :) ***Before anyone says anything about pregnancy I'm a virgin***