Anna,
Hun, look the therapist right in the eye and tell the God's honest truth about EXACTLY how you feel. You're paying for the session. You have the right to do this. Honesty is a must, Hun, so just speak your mind.
The people above gave you really good advice; namely, hang in there and see how it goes. If, after several sessions you still feel uptight, say so to the therapist again. Take it from there depending on what they say.
At some point, you may have to switch therapists, but give this one a good and honest chance. Personally, I think you will eventually get in the groove with therapy, but it really can take a while. Remember, these issues are really heavy, and it can take a while to get comfortable talking aobut them. Really. I feel the same way you do. Many of us do. You're NOT the only one! Hang in there, Hun.
Good Luck!
Hugs.