This won't be what you want to hear. . And I am sorry.
Walk away. Run if it makes it easier. If you can be his friend, by all means.. but I know how hard it is to bury love and adoration. Continuing on with a sexual relationship will only make it harder.
I am married to an addict. 8 years of the roller coaster of rejoice and relapse. Wait it out.. if he stays sober for a few years.. then try for something. Until then.. you may be chasing a nightmare. And the hurt it causes your heart..its unbearable. Avoid it. Protect yourself.