Hi element,
Good for you that you have the courage to recognize that you are in alot of discomfort and you are going to getting some help. After all if you had alot of pain in your shoulder or leg, you'd go to a doctor. This isn't really all that different.
I'm guessing that you will visit your family doctor. Tell the dr. that you would like to talk to a dr who specializing in dealing with the kinds of the things you have described.
A psychiatrist/psychologist will often begin by asking you what is bothering you. Believe me, you aren't going to be able to tell them anything that they haven't heard before. Also, as was said earlier, they also ask for background info, like where do you live, your level of education, do you like school, do you have bros/sisters, etc. They are trying to get an overall sketch of you.
Like any relationship, it will take some time for trust to develop. If you find yourself feeling too nervous to talk, then I'd tell them just that.
You have your whole life ahead of you and you can get help so that you don't have to feel the way you describe.
Hope this helps. Also hope you post and let us know how you make out. If you have any more questions, I'm sure that people will respond.
mermaidmo