Should I be worried if the spans of my cycles vary widely from 2 days one month to over 8 days the next month?

It may be time to talk to your doctor if:

You haven’t had a period for 90 days Your period suddenly becomes irregular You have a period more often than every 21 days You have a period less often than every 35 days Your period lasts for more than a week Your period becomes unusually heavy You bleed between periods Your periods are extremely painful