I don't like drinking but my boyfriend does

I need help guys... my boyfriend just started drinking occasionally with his friends. I hate drinking my dad was an alcoholic and did time for DUI's. He knows this... he promised me he would stop drinking and then broke his promise and drank with his friends and I forgave him for that.. He then told me he was sorry and he knew he hurt me but then yesterday he did it yet again with his friends.. I honestly feel betrayed and hurt, this is the 2nd time he's broken his word.. his word obviously means nothing to me and keeping my trust isn't something important. He apologizes each time and says he understands if I can't do this anymore and the problem is I love him and I don't want to leave him.. but I everytime he drinks it feels like he's betraying me and it hurt a lot... what should I do.... I don't know what to do... we've been dating 4 years and I love him but this seems to be like the thing that will break us apart