I had similar feelings last year when I started therapy. I never thought that It would help me I was afraid to open up myself. But after a couple months there was a change. Changes take time nothing is instant. Don't be afraid to tell the therapist your concerns, they are there for you, you are not there for them. I hope that things get better for you and the you find the help you need here.
Hello and welcome to the forum,
Just go in hoping for the best. You play a more important part in your therapy than the therapist does. Are you taking medicine right now for the bipolar? Treatment of bipolar is progressive and it gets to a point where you are not treating the bipolar as a whole but instead treating the aspects of it that make it worse. I am sure you have learned a lot about yourself and you need to take that knowledge in with you but keep your mind open to learning more. Go in prepared but with no expectations.
They don't have all the answers, none of them do. The answers are in you but they can help you to find them if you give them a chance. Listen to everything and give good feedback. Try to let down your guard and open up. Take what you need from the sessions and leave the rest. Working with a therapist is a two way street. You have to help them or they cannot help you. Keep coming back here and let us know how you are doing. This can be a good place to check in from time to time because there are a lot of people on here with various types of advise and experiences.
Good Luck