Delayed periods, dark brown discharge, no smell and slight pain in left side lower abdomen and gas?

irregular periods: Irregular periods are one of the most common problems obgyns treat. If this is one time problem it usually resolves on its own. If this is a recurring problem you should be evaluated. Infections ; hormonal changes can cause spotting. If there is a concern for pregnancy then do a home pregnancy test . There are many options available to help regulate the menstrual cycle. Schedule a visit.

Variety of causes: There could be a variety of causes related to fibroids or endometriosis or other explanations. It is best to see your gynecologist for an examination and possible lab tests including diagnostic imaging.