You might want to just check out Prochaska's model of change. It would put you in the "pre-contemplative" stage; in other words, not ready to make a change. This is okay, it is where you are at. One thing you can do, that actually can lead to moving into another stage (and it isn't a one way street, or about success or failure, just about change or not changing) is to begin to educate yourself about what you are doing. Read about substance abuse, just informational stuff from good resources, or about something else that is causing you problems in life; crack the door to thinking about it without any commitment to do anything.
One big issue with substance abuse is that it really does get in the way of making any other changes you might want to consider, though there is nothing wrong with say, reading about careers you might be interested in, we all have our own path. You will know when you are ready---the pop book is called "Changing For Good"---but you could just read it and blow it off, throw it in a corner and look another day. What he did was he looked at all the research done on and all the theories about how people change and all the therapies used to promote change, took what was the same in all and distilled the information.
Keep talking to us. Good advise is not always helpful. We are still here for you.