In my first session, I described my situation to my therapist and asked if I might be trans, she said, "That's for you to decide. I'm just here to help you explore your mind and heart until you find your most authentic inner self without all the masks and deceptions that we all build up in dealing with the outer world. Then we will both know the answer and we can determine together what to do about it." I thought that was a very good answer.
In the sessions since then, we've talked about all sorts of things, many of which seem totally random and trivial until some deep memory breaks free and reveals a little bit more to me about myself. I think of it as the "hit and run epiphany".

As a result of therapy, I've come to discover that I really do feel more like a woman than a man, moreso every day, and that pursuing transition is becoming more important to me with every new self-discovery. I have decided that I definitely do want to proceed with HRT and RLE. I'm still undecided about SRS, but am starting to lean in favor. Without my therapist, I think it would have taken many more years before I could bear to face the truth of my situation and own the idea that I just don't feel any attachment to the male social role at all. In fact, without therapy, I would probably STILL be trying miserably to prove to myself that I am the gender my anatomy would suggest...even though it feels like a lie.
The most important thing about a therapist is to find one you feel you can be honest and open with...especially with the parts of your life that you may be uncomfortable talking about. You'll have good sessions and bad sessions, happy sessions and angry sessions, but I find that I generally look forward to the next session...even if I bawled my fool head off in the previous one. I always come away feeling better and more self-aware in some small way or another.
So, keep a positive attitude going in and give yourself several sessions to learn if you can get comfortable with the therapist...and find a different one if you just can't open up. Remember, everything you say in session is legally protected and completely confidential (with very, very few exceptions) and no topic is necessarily off limits to discussion in session unless you want it to be. Be honest with the therapist and with yourself. Whether you discover you are trans or cis, crossdresser or fetishist, or something else completely, it's all good and therapy will help you figure out who and what you really are. That's really the whole point of it all.
Peace.