16 y/o. my period this month is normal but has stringy tissue like substance as discharge. it's bloody and kind of long. what is this?? is it normal?

Common problem: 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.