I know how it is. Until four months ago, I never told anyone about my deeper feelings and/or thoughts. I changed, though. To list how I became more open:

1: I became depressed, hence I had to talk to someone.
2: I found people who I could talk to about this. Don't tell your problems to anyone, some people will use it to bring you down.
3: I'm not afraid of people's reactions anymore. So what if they don't like what I tell them? %#@&#! those shallow bastards.

It's all about the right attitude, and having the right people to talk to. If you can't find anyone receptible enough amongst your friends, talk to a shrink, or someone similar. Currently, I have told maybe 50 people in my real life (friends, family, shrinks, teachers, etc.) about my problems and innermost thoughts.