hello.. First of all you didnt mention your age. yes you are right, the symptoms known as spotting. It simply means the exessive bleeding during your menstruation, the condition termed as menorrhagia. these exessive blood discharge clots therefore the clotted blood is dark brown in colour. It may be normal in your menarche (start of menses) or durind menopause, also in conditions like uterine fibroids, as withdrawl bleeding, or in some bleeding disorders but you should consult your gynacologists if the bleeding continues or the abdominal pain continues.. Your doctor may suggest you to get abdo-pelvic sonography to rule out PCOD, fiboids or some pathological tests to rule out bleeding conditions or endometriosis or pelvic infections.. take care..