What Is The Reason For Not Getting Proper Periods?

Hi Doctor,
My name is ruby 32 years old Im using Belara pills one years last saturday 10th december I have menstration only one day the second day brown third day brown blood again then after that my menstruation its gone. Then Im going to Pharmacy as the staff what best medicine so that I got menstruation again He give me Primolut Nor 10 mg table I take 1 week now but nothing come my menstruation. Then I have sex my husband twice but continue drink medicine primolut. Yesterday I buy pregnancy test but the result negative. Then I buy pills belara I take one tablet last night. What happen my menstruation ? It possible I got pregnant? Now I continue to take Primolut tablet.