What is wrong with my brother?

Ok my brother is 19 years old and we have a place together. He has a job but his hours have declined alot. His past 2 jobs, his hours have went down and he cant afford to pay the bills as a result. He starts out with a good amount of hours but then it just goes downhill. He wakes up at like 2 oclock, gets on his computer and plays a game all day and all night. Goes to sleep at like 5 or 6 in the morning, then does the same thing all over again. He never comes out of his room, only to use the restroom or get something to eat/drink. He has no friends, and if he does, he met all of them online through this video game he plays. My family thinks there is something wrong with him but we dont know what it could be. I suggest having him to talk to a professional but my mom doesnt want that to happen. whats wrong with him?