What Causes Irregular Menstruation Flow?

I was bleeding for 2 weeks straight so i went to doctor and he put me on medroxyprogesterone 10mg for 21 days started taking right away bleeding stop for 2days. After that started spotting on and off for for a week then started light bleeding for another week the after that started bleeding heavy for 3 days after that started light been bleeding for over a month now and have not stop. Is this normal? Really need to know?