Been with DP 3 years, lived together for the past year. He's never been aggressive towards me but has shouted during arguments etc (but don't we all) and I noticed he is an aggressive driver but thats not directed at me. Anyway I have noticed he gets a little more aggressive after a drink but as he doesn't drink much it was never really an issue but for the past few months he's gradually started drinking more and more. Last night he came home with a big crate of lagers that he said were on offer. He opened one as soon as he got home and drank it within 10 mniutes and opened another. He offered to me to help myself but I said it was too early for me and I'd join him with a drink later.
About an hour later I went for a shower and by the time I got out he'd drank 6 cans altogether and his mood had totally changed, he didn't speak to me as I entered the living room or even look at me. I sat down next to him and snuggled upto him as usual. He didn't react or put his arm around me or anything. I asked if he fancied watching a movie with me and he said "who's Dave?" 
so I said "Dave who??" and he snapped "well how many fucking daves are there??" so I sat up and said "do you mean dave from work?" and he said "I dont know, whichever dave keeps texting you". I realised then that he'd been through my phone while I was in the shower and the texts from this dave were all work related apart from one which was regarding a work night out which he'd sent to a few people. I said "He's just someone I work with" so he said "and how often do you see him out of work?" so I said "never" so he shouted in my face "dont fucking lie to me, ive seen the texts". I stood up and went into the kitchen to get a glass of milk (and to get away from him) and he followed me and put his arms at either side of me so I was between him and the work surface and then said again in my face "how often do you see him out of work". I tried to gently move his arm away so I could leave but he wouldn't move and so I said "look, if you just talk to me properly instead of shouting I'll go through it all with you" so he shouted that I couldn't even look him in the eye and so I said that was because he was intimidating me and I wanted to leave the kitchen. He eventually moved but refused to speak to me for the rest of the night whilst repeating "don't think you've got away with it" etc.
I dont know how to deal with this. we've hardly spoken today but that is a side to him I've not seen before and I dont like it 