Your boyfriend is ambitious and it's telling that in the post, you seem to regard his ambition as perhaps not necessary ("already got a very good job"). You also seem to have no interest in what interests him. In other words, you're not a supportive partner. You're not actively sabotaging him, but neither are you invested in his success.

Your behavior right now (not taking to networking, setting up the "on the couch with me or out nurturing your career" choice, your emotional reactions) is not making an argument to him that you're a part of his life that's as rewarding as the career part is.

I think this is why you're getting upset. Because your boyfriend is already confirming your fears that you two are growing apart, and because you know that if you asked him to choose, he would not choose you.

Referring to the job and social life he's thrown himself into as "that life" and "his world" and "this part of his life" suggests that you have drawn a bright line between the thing that fulfills and energizes him (his career) and you.

If your boyfriend has been drawing that same line, then don't be surprised if he breaks it off with you.

He may want a life where his romantic partnership complements, not competes, with his extraordinarily fulfilling career. It sucks and it's unfair that what you two each want has shifted over time, but it happens in your 20s. It's part of life.