Welcome, Heartbroken. I am sorry for what you are going through, sadly it is a common story here and as long as there are drugs and addiction of any kind in the relationship, there is no happy ending.
He may ask you to hold his stash, but what's to say he doesn't have a second stash hidden? He would not be the first to manipulate a loved one into thinking they had any "control" at all over their addiction. It's an illusion to think we do, the sad truth is that nothing we do or don't do, say or don't say, will change anyone who is not willing to change....and willingness is shown by actions and time and not words.
My son is the addicted loved one in my life, but I think we all share the same pain of trying to save someone we love until we ourselves get sick with the trying.
Take a read around, especially the stickies at the top of this forum and you may see some familiar stories. Also, there is a book called "Codependent No More" that helped many of us discover why we were so drawn into the darkness of addiction and what we can do to make better choices and live a healthier life.
Again, welcome. I hope you will stick around and know that you aren't walking alone anymore.
Hugs