(((Hugs)))

Your boyfriend is 21 and if he's been socially anxious in the past, drinking is probably helping with that and he is enjoying his time with his friends now. He is experiencing new aspects of life and these might do him well, or they might teach him unfortunate and sad lessons. I would try not to focus on what he is doing and try to build your own experiences and life. Take this time to battle and conquer your anxieties. He is a big boy and is making big boy decisions which he's entitled to. He doesn't want you as part of this new journey and you owe it to yourself to accept that and start building a life which makes you happy. Don't count on him coming to his senses and coming back soon....don't be quick to trust if he does. When someone tells you they've grown apart from you, trust their words and respect yourself enough not to be around someone who feels this way.

Breaks ups are sooooo hard. It's like a death but worse because the mourning isn't as accepted and the person still breathes yet you cannot hold them or be with them. It's horrible. You feel bad now and should honor your feelings. But they won't last forever I promise. (((Hugs)))