I've had my period for 12 days now an getting a lil concerned an i'm currently not on birth control but i also had a miscarriage a few months ago?

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.

Please get examined: You should get examined. Some time one gets Dysfunctional Uterine Bleeding because of Hormonal imbalance. And sometimes one needs D&C for stopping the prolonged Bleeding.