Talk to Gynecologist on Abnormal Periods

Hey there! I've been facing an abnormal period issue for quite some time. Sometimes my cycle even exceeds 30 or 35 days. The flow and the colour aren't right. I barely have any flow now even if I have it hardly lasts 2 days and the colour is dark brownish. And sometimes, I just have spotting throughout my cycle. I don't have any other issues like weight gain or facial hair. I went to the doctor last September and she told me it's fine and she prescribed me some medicines after that for just 3 to 4 months so that my cycle would be normal and after that duration it would again become like this. So could you tell me what I should do about it?