A dysfluent pattern of talking in which nervousness or anxiety is the only time it occurs is not a "typical" stuttering pattern. Dysfluencies occur due to various etiologies. It may be a secondary behavior to your nervousness due to your social anxiety. Confidence does not usually "fix" a typical stutter. It doesn't mean that a speech therapist cannot be useful, but, working with one along with a qualified psychologist, both of whom work together from different angles may be useful. A consultation and/or evaluation from each specialist may give you some useful tools.