
Differential time!
Joannie, it my or may not stop. If this happens chronically (alot) then you have a problem and read on. Otherwise (unless it is excessive bleeding) then you should be OK.
You may have an irritation of the cervix or something more serious like a coagulation problem. You should get this looked at by a doctor. I could see it being a cervix problem because of anovulation (you haven't mentioned getting pregnant).
See if you can get a hysteroscopy to check for polyps. This would be another Cervical problem that could lead to cancer.
Also ask the doctor for a thyroid test (depends on your age, but not likely).
You should ask lobsang if I'm on the right track.
:P