Abuse/love

Long story short my boyfriend of almost 3 years doesn't so much have a drinking problem but when he does drink he can be rather abusive. After everything is all said and done, we both act like it never happened. We both do love and care about each other, but whenever I tell him how he is when he drinks, he doesn't believe me. His best friend has told me he knows the kind of person he is when he drinks but won't tell my boyfriend to his face. What do I do? Please help!!