I am not sure how old you are - but you may be too young to know how to deal with some one that has a drug habit. I know this personally, because I ended up breaking up with someone when I was 22 because of a drug habit.
Honestly I didn't realize it was due to the drug/alcohol habit at first. I broke up with him because he would be 2 hours late to pick me up (even after once when he didn't show up over an hour, I went out with my friends); he wouldn't have money even though he had a good job. He went to "camp" for drunk driving - which I didn't know about until after the fact. He was a real sweet heart aside from these things. But finally I couldn't deal with it and didn't know how.
He kinda tried getting me back - sending me two dozen red roses and one white for hoping I would stay with him. I went over his apartment to talk with him and while sitting in his room while he went to the bathroom, I saw a small piece of paper - I folded it back up along the creases and realized what it was - a packet for cocaine. I showed it to him and then walked out and didn't ever contact him afterwards. I realized he had a drug/alcohol problem and I wasn't capable of helping him.