My husband was exactly the same.... just sitting quietly at home and drinking, not causing any trouble, going to work and having a great career. The drinking increased so slowly that neither of us really paid any attention. Now 15 years later he is a full blown alcoholic and NEEDS it. He's already started losing his reputation, is in great danger of losing his job which means also losing our house. Next time there's a police check he will very likely get arrested for drunk driving. And if a miracle doesn't occur soon then he's going to lose his wife (me), too.
Thank God we don't have children. I'm having a tough enough time with the way he's handling, or rather mis-handling our two dogs. I can no longer trust him alone with them. I can't even trust him to take off his muddy shoes before crawling into bed and passing out!
And he is doing harm. He is harming his health. Alcohol is a poison. If alcohol were discovered or invented today there is no way that it would be allowed to be sold without a doctor's prescription. And by harming his health he is harming any longer-term future with you.
Keep reading and learn more about alcoholism. Unless your boyfriend recognises the danger and does something about it, your future will best case end up like mine, and worst case like many of the other people on this forum who are in serious physical, mental and emotional danger.