My period came 3 weeks late last month but only lasted 3 days when i usually have a 7 day cycle. 1st day was light,2-3rd was heavy.???

Irregular menses: There is a wide variety of reasons to have irregular vaginal bleeding, including pregnancy. Have you done a pregnancy test? If not,then that would be a good place to start. Is anything happening in your life? Increased stress, weight loss, weight gain, infections, chronic illness...again the list is long. You do not mention age but if older could be headed towards menopause.