You will find lots of people here that understand and can offer advice and support.
From what you describe, he sounds like he could potentially be an alcoholic. The disease is progressive and it doesn't sound like if he is an alcoholic that it has progressed to the point that he is likely to see it as a problem. It doesn't sound like he drinks an unreasonable amount around you, but the fact that he notes that he doesn't drink that much when you're around... makes me wonder how much he drinks when you're not around. The fact that he drinks quite a bit while trying not to drink very much... yeah, that kind of is a sign of alcoholism. The fact that it is causing problems in your relationship and he's still unwilling to quit is another sign.
"I dont like that he gets affected by his alcohol use (even if he doesnt get drunk, for sure he gets relaxed and a bit more happy because of this)."
Personally, I don't see him being a bit more relaxed and happy due to the alcohol as a huge problem. If he was angry, mean, etc., that would be a huge problem for me.
Having said all of that, I think it's important to try to not worry about him or what he is doing. You can't change his drinking. He's an adult and can drink if he wants to. What you can change is this: "I am obsessing about this day and night and cant study or work because this is on my mind all the time ."
His drinking is his problem. You obsessing is your problem. It is crucial to identify what is yours to deal with and what isn't.