What were you doing when he bit you?

Contact a positive reinforcement ONLY behaviorist through http://www.iaabc.org/. You definitely need professional advice for a biting dog, especially with a baby on the way. Without any of us actually being there to observe the situation, and without any of us being behaviorists, it's unconscionable to give you any serious advice. The only advice I would feel comfortable giving is what to do to avoid provoking him, not how to resolve the aggression itself.