Age 42, always had normal periods. period came 11 days early. no other issues.

Depends: It is not uncommon to have an abnormal period once. Stress strenuous exercise, age medical problem like diabetes or thyroid condition are a few reasons one might have repeated episodes of abnormal menses. See your md, if appropriate do a pregnancy test.

Many possibilities: Many possibilities. Pregnancy, changes in hormones, normal change. It could also be other things like polyps or even some bad things. However, it is probably nothing. So impossible to tell. You should see your gynecologist.