I had my tubes tied 6yrs ago! Since then my periods have been normal! I started wk ago very Lil bleeding lasted 4days! Started again 2day heavy w/clot?

Not ovulating. You are likely did not ovulate this cycle. Not releasing an egg each month can make your periods irregular. If your periods were regular, stress may have caused you to not ovulate this cycle and caused your period to be irregular. If it happened just this one month, your periods will likely return to normal. This is normal in women not on hormonal birth control.