yep hug to you...
You know, I know this is going to sound mean maybe but in my opinion i think you need to leave him or distance yourself from him. I am telling you this kind of stuff can change ruin your life just as much as his. it's probably like you're on the stuff even though you're not... cos you have experience all the highs and lows with him. Doing what he is doing is a selfish act that he can't even help. he is taking life and you for granted and that energy can shatter yours and you deserve way more than that...
I know leaving someone you love is hard or even distancing him but you need to do something to make sure that you are protected. i mean.... slowly you'll be just as consumed on the drugs as he is.... cos you'll just be hoping to get your next hit of cleaness just like he is waiting for his next hit of cocaine....

good luck and i am sure you'll have the best for you... and that you'll be strong enough t do everything you have to.....

i've been where you are... Best thing you can do is support him and offer him an alternative, if you mean something to him chances are he will change his addiction. but don't leave the relationship until you have offered your helping hand...

I will pray so that he comes to his senses and notice that he is not only hurting himself but
the peolpe around him...

When I was your age I was in a relationship of 3 years with a person that was addicted to coke.  
It was a complete rollercoster ride.  Emotionally and phyically I was wiped out.  He didn't want to lose me, so he went to counseling and the counselor told me that he was doing it for me and not for himself and that he would suggest that I leave him.  I loved him to much to just leave him.  I tried everything to help him.  Key word again was I tried, while he would be getting high with his buddies.  

Like you, I seen crystal clear how this relationship was going to end.  Unlike you, my empath heightened.  I would know where he was in neighborhoods I didn't even know, even the exact house and cars he was in.  It was crazy.  I would go looking for him and it's as if I wasn't even driving.  A lot if other strang happenings, but to many to list.  Today, I'm not as sensitive as I use to be.

Anyway, we were once on vacation and everything was finally perfect.  He was talking about "forever" and without thinking (as if someone else spoke), I said, as soon as we get home we're going to break up and be friends.  I felt such release.  

Relationships should be about love and all that good stuff - I didn't think this was a relationship of love, but like a purpose.  At least that's the only way I could explain it.

Big hug - Rose

Sweetie, why not take him away, far from the place where he lives to die!
Big hug!