Stopped using nuvaring and was still having regular cycles. now 3 months later period stopped. negative urine pregnancy test. is this common ?

Very common: 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. If there is a concern for pregnancy then do a home pregnancy test . There are many options available to help regulate the menstrual cycle. Restarting NuvaRing would correct the problem.