I used to be at least semi-hikki; no friends, no leaving house, spending almost every second of the day in my room, barely speaking to anyone, ever, at all...
Eventualy the stress of so much time going by while i acheived nothing became too much, and so I made the decision to re-join society.
I started out with smaller things to prepare me for living a more normal life. I went for walks, I talked on the phone, I went out shopping and collected new clothes to wear in public so i'd feel more comfortable. After a while, I started a course. At first, it was kinda hard, I was uncomfortable around so many people etc, and every day I did something embarassing [tripping over, saying stupid things, other social blunders]... the bad feelings slowly went away, and sometimes i even enjoy going to my classes and being with friends.