Hormonal fluctuations, stress, too much of exercise, weight loss or weight gain all can lead to irregular periods. The chances of pregnancy are very less since you have been having your periods though a little early. Are you also having other symptoms suggestive of pregnancy like nausea, vomiting, sore breasts, nipples, increased urinary frequency? If you are doubtful about pregnancy seeking the opinion of a gynecologist will definitely be helpful. A complete clinical examination and investigations like pregnancy test may be needed. Do keep me posted.
Best of luck and regards!