I think my bf is using again

My boyfriend and I have been together for almost 4 years. He got addicted to lean (cough syrup) in 2013 before I knew him. When we started dating in 2015 I didn’t know about his addiction. By the time I found out it progressed to pills and eventually heroin in 2017. He OD’d 3 times that year, I had to do cpr on him once. The last time I told him I couldn’t do it anymore, I was going to leave if he didn’t get clean. And he did, he took it seriously and we went to therapy together. He was doing great until about 2 months ago I noticed him acting kind of secretive. Last night I looked in his trash and found lean bottles. I cried for like an hour. I haven’t talked to him about it yet. I want to be with him long term, he is such a good boyfriend. He works a good job, is so kind to everyone, and treats me like a queen. But he has a lot of depression issues and always seems to fall into addiction. I love him so much but I don’t know what to do anymore