Since you enjoy your alone time, have you reflected on WHY you feel this way? You have asked if it's a disorder or if something is wrong, but have you seriously asked why, and thought it out. The answer could be as simple as other people and their incessant noise drive you insane and coping with it is draining you. It could be as difficult as you don't know why, but others just irritate you. Either way, talking to a counselor about it could help. I know when I went through my alone phase, I did it because I was depressed. I didn't feel depressed, but I just didn't want to deal with people. When I was alone, I was happy.