Should I trust him again?

I have been with him for almost 3 years. He is drugs-taker since the first time I get to know him. He even sell those drugs to other people. But he had promise me for not to take drugs again. Yet he break the promise he made to me and always ask for my forgiveness every time. Sometimes I feel should I ever trust him again that he really can get rid of this. I been hurt countless time and I fear i cannot accept another disappointment again. But I hardly have the courage to leave him as I still love him dearly and perhaps too rely on him. Now, I dare not to take the step of believing him as I fear when i have the hope, he will again leave me heartbroken. He did said, love a person should accept for who he is. Is it what he said is true that i must learn to accept him of taking drugs? Besides, he also said that many people are taking drugs so I should learn to adopt to the environment. Yet I barely can accept the fact that drugs are common nowadays. I confuse and insecure whether I can really live the rest of my life with happily with drugs-free life.

is not a point where you are suppose to trust him anymore..but is about time you have to take matters in your hand..because he had been multiple time to discourage you and while still begged you to forgive him....so 1 2 3 time..sure...and what make you think the 4th time will make any different....im sorrt to hear that your bf are like that ..but it time for you to do what you feel is right..it take love to earn love.. and if you ever think about your future with him....then i dont know because im not really here to tell you to break up with ur bf...im sure no one want to do that..but the main question is would u rather get hurt once and for all or u willing to get hurt over and over againt...and by the time you are done and no more hurt feeling that when u will stop loving him...and people dont reallize what they do wrong..and when they did reallize that is wrong..which is already too late ..but good luck!! =)