Needing to vent

I've been with my fiancé for 7 years. I've lived with him for the last year. We seem like a happy couple at most times but I'm far from happy a lot of days. My fiancé is an admitted prescription drug abuser and I've known about it for about 3 years. I'm 100% against illegal drugs and it use to be a big deal breaker if I ever dated anyone who did it. But by time I knew my fiancé did it we have been together 4 years and had been engaged for 2 years. It's not as bad as it used to be but any use to me is bad and makes me so angry when I find out. He's never hurt me physically or mentally and he pays the bills every month with little to no issue. However, because of this problem he never has any money left over after bills and he gets paid very well. We're coming to the end of our lease and I'm seriously thinking of leaving him bc I can't deal with it any more. I'm already taking anxiety medication. He's thinks he doesn't have a major problem anymore and blames any use now on a bad shoulder injury that happened years ago. But about 3 months ago he was pulled over and charged with a DUI that we are still going through courts with. I don't know what to do. I love him more than anything and see us having a family, which we had been trying to have. If I leave, he'll be left with nothing bc the vehicle he drives belongs to me. Without it he'll have no job, no money, and no home. I can't do that to him but I can't live like this anymore either. I just don't know what to do. 😔