openness

I've been realizing lately that I have problems opening up to people. I don't have problems making friends, or caring about people. Dont' get me wrong, I care deeply about a lot of people. At the same time I like being able to hold people at a distance, to keep parts of myself from other people. I think it's partially because I'm scared that if I open up to someone completely, I won't have any defenses left. I also think that part of it is also that I have a bad tendency to just close off and shut down when I feel out of control, or threatened, or scared. It feels easier to shut down and not feel anything than to feel hurt.
For example, my dad called today. We talked about the fact that I am flat broke, mainly why I didn't tell my parents I didn't have money. He asked me how I was doing, and I just shrugged it off and said that I'm doing fine. School is busy, but I'm fine. What I really should have said is that I'm going through a rather difficult time emotionally, I have no motivation to finish school right now, I'm trying to talk to people about it so I can work through it and function again but it's difficult for me to ask for help. It's difficult for me to admit that I'm having a hard time. But I didn't. My parents love me, I know this. They managed to survive me coming out to them three different times, which is quite astonishing as it is, and they have always supported me in many many ways. If anything I should be able to open up enough to just say that I'm having a hard time but I'm getting through it. But I couldn't.
And of course the strangest thing is that I'm willing to just throw this up on the internet where anyone can read it. There's something to be said for a sense of anonymity I suppose.