I don't have any great insight here, just a suggestion that you focus on "I-statements" ("I'm concerned about your drinking" ... "I've noticed that you've been drinking more lately" ... "I'm worried about your health" ..."I'm trying to understand what's been going on because I notice you've been drinking more" ...) rather than "you-statements" ("you have a problem" ... "you might be an alcoholic "...).
If you have a specific incident in mind you could use it as an opener ("When we went to the Johnsons' party, I felt really awkward because it looked like you were having trouble talking clearly") and then move into more general concerns.
I think standard advice is also to avoid the words "always" and "never".