Glad you came out of the shadows and joined us, Barkley.
I am sorry your heart is broken and I hope you will find some comfort here.
You are young and say this is your first relationship, that may make it harder right now, 6 years is a long time and I'm sure you had dreams of a live together and living happily ever after.
Sadly that rarely happens when addiction moves in, you are wise to let this go even if it hurts.
The "strangely wrapped gift" that Zoso referred to, and that I believe comes to all of us, just may be that the lessons you learned from all this will help you in future relationships. You may spot the red flags sooner, know what it really means if they have addiction "issues" no matter how they may downplay it, and you will know a healthy relationship when you see it...the kind that does have "happy ever afters".
Stick around and know that you are not alone here, we all walk with you.
Hugs