Drinking too much(semi-long post)

I'm 22, my boyfriend is 27 and we've been together for a year and a half. In the beginning of our relationship, he would have a beer/drink or two here and there when we were out together. About five months in I started spending weekends at his place and he would ask me if it was okay if he drank, I agreed. Still no big deal. We got drunk together once around this time last year because I wanted to do it safely and see what the hype was. I feel like after that day, he has gradually been drinking more. I mean killing a regular sized bottle of vodka(not the skinny one) within a couple of hours every weekend. He's in Grad school and sober all week until Thursday/ Friday depending on his schedule and then back to drinking. When r schedules coincide I'm usually at his place for 3 day weekends together since we live a few hours apart. He spends at least one of those days drinking, gaming, annoying/fighting/crying/professing his love to me and staying up until 6am before he stumbles to bed and most of that next hungover. Even had a few instances where he's thrown up from drinking, just to go back to it. I've talked to him about it and he says that I need to drink more. I talked to him again and he said he'll cutback. His idea of cutting back was switching to the 4 litre bottle of wine and killing 80% of it in one night alone. It makes me sad. He's gained weight, not eating right, neglecting his hygiene and it's interfering with not only the relationship but our once overly active sex life has faded(he has noticed because he can't perform)I'm lucky if we get to be physical once within 72 hours. I don't what else to do but talk to him about it one last time and involve his mother after that.