A few things come to mind…
The selection of a compatible therapist is important. Some folks don’t have the knowledge concerning gender issues and others don’t have the sensitivity for it. That doesn’t make them bad therapists, but it does mean that their help in your situation wouldn’t be helpful. Suggestion here would be to check in with any organizations or support groups in your area for recommendations. Curious about the thought of gender dysphoria after only one session. That seems premature unless you exhibit the criteria almost exactly. In the course of my engineering career I’ve done some work with process forensics. The process is that you gather the facts and that points to theories and ultimately to conclusions. Deciding early on what possible conclusions are tends to lead one in the direction of finding things that support that conclusion; often at the expense of missing or ignoring other useful pieces of information.
Sorting out ones gender identity is a journey. Journeys take time. There are no shortcuts. It took you X number of years to get to this point, so it isn’t going to be sorted and unraveled next month and perhaps not even next year. It is important to stay the course. What’s the saying? “All will be revealed in the fullness of time.”. Perhaps not all, but mostly.
Lastly, I’m curious about the “wrong reasons”. Can you explain that further?