How Do I Leave My Drug Addicted Husband?

Can you go and live with your parents for the time being until you can get through school?  Are they aware of the situation?  If not, I think you need to sit down and explain the situation to them, and then ask if you can move back home. 
 
It does sound like he's trying to overcome his problems, and you need to be supportive, but at the same time, you do need to get away from that.  maybe if he realizes that he's about to lose his wife and kids because of his addiction, it will be enough motivation (even if you've threatened this before, it is just a threat until you actually do it). 
 
If going back home isn't possible, then the only other thing to do would be to go to social services and explain the situation to them.  Find out if you and your husband separated (but not divorced, since I'm assuming you would go back to him if he cleaned himself up), if there are any programs and assistance for you and your kids. 
 
Unfortunately, keep in mind that as a de facto single mother of three, that finances will always be a problem for you, even if your husband were to pay child support.

I could have written that myself.

I have given him numerous chances and now I am just done.

He is doing the exact same thing he did the past previous times I wanted to leave out of disparity. "I PROMISE I'll change". Instead, he just gets better at lying, sneaking and doing everything behind my back.

This time he asked me to write a list of what I want him to do to change.

Even though the thought of doing so made me nauseaous, I did because he is so predictable and I knew it would either prove that he was sincere or prove what I already knew...he wasn't going to change..

The whole time I was reading it to him, he was arguing my stipulatons.
Stipulations that NO wife should have to write down directions for to have a good marriage.
I am glad I wrote the list he asked for. Now I know what to do.

Leave.

I am going through a similar situation. I am a full time student and my husband is an attorney...I think he uses his title to justify drinking and smoking pot every night...Half of the time, he does cocaine, even though I have told him so many times that I don't want to do that! We used to party a lot together, but I am over that and just want to live a guilt free life.  I want to have kids someday, and he does too, but I am scared that I will be pregnant and he will still be partying everynight.  I don't mean to make myself sound like an angel, as I am not, but I am so over the life style.  I can't stand to see him laying on the couch stoned night after night.  It makes me totally unattracted to him and also makes me resent him.  He knows how I feel about this, but he continues to do it.  I love him, but  I am not happy.  He keeps saying that he will change and that he is sorry, but he always goes back to his old ways.  I think I know what I should do, but I am so scared to go through with divorce!!!