Drug addict

So I've been dating a drug Addict since august 2014 he said he was gonna quit but never has he is always asking me for money or wanting to go get it I love him but I feel like he is never gonna get better. Has anyone here ever dated a drug addict and how did it affect you and did u leave or stay???? By the way he is addicted to herion but if you saw him you would have no clue