First thing, your actions do not cause any relapse. He chooses to use. He relapses and uses drugs. You don't make him. You don't force him. Unless you're holding a gun to his head, any concept of you being to blame for him relapsing is false. If he's bringing it up, he's a chickenshit who won't face his own addiction and no, then he's definitely not trying.
I struggle with the same thing. It's been about a year and a half for mine, and I went through a pretty hard depression. I lost interest in him. It's like he killed the love in me, the compassion, the empathy, the loving feelings, the passion, the joy. I actually told him once that I didn't think I loved him anymore, that what I was feeling was numbness.
I needed help for myself. It wasn't all on him. I have seen someone on and off. I don't do meds (I refuse to do antidepressants for my own reasons--no, I'm not a scientologist! haha.) But, the love and emotion that I once felt for him is slowly coming back. He's been very patient, very understanding. He has struggled a little with it. At one point, he said to me, "please come back. Come back to me."
It's taken effort on my part. It felt like work at first, I'll admit. To reach out and touch him, to initiate a hug, a kiss, God forbid sex. It really did feel like I was going through the motions sometimes, but it got easier and the more I did these loving things, the more I enjoyed them and started to fall in love with him again.
It began so fragile. It's getting stronger. I want this to work, but there were times when the idea of giving up and living apart was such a wonderful dream, a fantasy. I even used to wonder what it would be like if he OD'ed and I was left in peace. I actually thought those things--not in a serious way, but for fleeting moments, I wondered about things like that.
He needs to get help. That trust will never never NEVER be rebuilt until he stops using and stops abusing your trust. Trust is not invulnerable. It breaks. And sometimes it breaks to the point of no repair. He has to work on it. He has to try. He has to want to be clean. He needs to follow through on his end and be 100% into it. You can talk to him about this. You can tell him this. But, he needs to really come to this on his own and be willing to walk that path of sobriety.
I know I sound like a broken record. Focus on you. Get yourself where you need to be mentally and you will be better prepared to deal with this and probably make some hard decisions. Only when I was ok with myself personally was I able to:
1. Set and follow through on boundaries.
2. Move past the anger.
3. Move past the bitterness.
4. Own my part in anything but let him own his piece as well (without apologizing or antagonizing.)
Lots of goodness in thought and prayer coming your way. Be well.
:ghug