Lots of thick brown discharge and had 2 cycles of period in 3 weeks. should i be worried?

Anovulatory bleeding: Bleeding often on like that without a clear cycle usually means that you did not ovulate. In that case estrogen continues to be produced and the lining of the uterus is get swollen and then pieces of it breakoff in an unpredictable manner and so you never have a regular menstrual cycle. But spotting and bleeding off and on. Good Health

Many options : 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.