18 and worried my boyfriend is drinking too much!

I could really use some advice! Me and my boyfriend are both 18 & have been together for almost three years. He suffers from diagnosed depression and OCD. Recently he’s been keeping a bottle of Vodka in his room. His mom was a very heavy alcoholic when he was a kid.

I tell him that I am always here for him and if he’s ever feeling down to never turn to alcohol but to come to me. Well how do I tell if he’s drinking too much? He’s going through those big bottles in a month span and he keeps getting more. I think he drinks a few days to at least once a week alone in his room when he plays video games.

I try to understand that he’s young and wants to “experiment” but shouldn’t that stop? Dose he really need to have a constant supply of alcohol when he’s chances of becoming an alcoholic is so high? I have talked to him about it, I told him how I felt but he still wants to drink. I don’t want to be controlling or anything but I love him and I don’t want him to ruin his life. I personally have only drank twice and I don’t find it fun so I don’t drink. Please give me honest advice! I am so worried.