How can I be more open and less fearful of my spouse in marriage counseling?

Marriage Counseling. Try to share your feelings in the session, tell your spouse and your counselor that this is very hard for you and that you are freightened. You will defeat the purpose of your being in therapy unless you can be forthcoming and this is an essential ability to maintain a close relationship. It is often very hard and you may also consider individual therapy for yourself to help. Best.
Personal counselling. I often recommend that partners have their own counselling sessions, and a personal counsellor, you may have issues to be worked on outside of the relationship before you can work on the relationship. If you are afraid of your partner, then trust needs to be built first, both with the therapist, and your partner.