Confused About How To Deal With Ex Heroin Addict?

So I have been dating this guy for 8 months now. He is kind sweet etc everything a girl could want a boyfriend to be. However, he has been 2 years sober from heroin and right now is not in N.A is not seeing a therapist. He isn't seeing anyone for help. He is kind of just battling it on his own. About 2 months ago he did coke once. Then did it again 2 weeks ago! now i tried to get him to go to N.A but he got very defensive and me being me (i try to help people) I kind of took offense to him getting mad that i wanted him to get help. I am just now sure exactly how i deal with this or what i should do about this. Him being a recovered heroin addict is no problem for me what is a problem is him doing coke. Any suggestions ?
Yea, but if he's doing coke then what else is he doing ? In my opinion coke is such a boring, cheap and plain way to get high that it doesn't even count. But I would expect it to act like a gateway drug and be the reason to move on to a harder drug after using that (coke). So I guess in my opinion it really does count. Are you sure he just didn't tell u it was coke that he used but it really wasn't ? It was really heroin that he did use and just said it was coke.? It's a reason why he got so defensive. Sorry I was no help. Good luck.