Topic : What to do now?

I am going back on Sunday to give my relationship one last go. My partner is addicted to marijuana and I want him to give it up. It is ruling our lives and im sick of it. I have realised now that I am an enabler and I am going to stop-I will be giving him the ultimatum of either giving it up or I will take our 14 month old daughter and move back to my parents. I love him so much and we have been together for 6 years but I am not happy and cant afford to live with stress any longer as i dont want our daughter to grow up in this environment. I am so scared that he wont change and ill have to leave-i have been with him since we were both 15 and our relationship is all i have ever known. how can i be strong enough to walk away from it all forever?? please someone help me i dont know who else to talk to.