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It sounds like he is still using, and I wouldn't even call it secretly using if he is flat out asking if you want to go get a bag cocaine. If he was in true recovery that wouldn't be a question he asked, hell if he was in true recovery then even if you spur of the moment brought it up someone in true recovery would say no.
Once someone has become an addict there is no turning back. No matter what the substance is and no matter what kind of crazy rationalization a person makes once he or she has become an addict then every substance is off the table. For example I am in recovery for heroin addiction and because I am in recovery I do not use heroin, cocaine, meth, weed, alcohol, etc. NEVER. No matter whether I am out, at home, with others, etc. NEVER.
I agree with DogOnCarol that you need to decide what is a boundary for you and what is not. For example, no drugs are allowed within my home, I will not socialize or even speak to someone who is actively using drugs, and that I won't continue to give several chances when someone is repeatedly not honest with me.
Once you decide what you find acceptable in a relationship then you will have your answer whether you want to stay or not.