Barking & biting for a 5 month old lab pup is really weird..Train your dog with rules, limitations & boundaries. When he tries to bark or bite - snap him out of the behavior by a nudge or a small but stern push near his hind legs. Alternatively, train him with the word "NO" - it should get under control. For further help refer to YouTube videos related to Cesar Millan - you should be able to get the situation under control.
Above all, when he does so & when you try to stop - ensure you exhibit calm and assertive behavior. Just remember, your dog will be the reflection/outcome of your energy. Claim your space and not let him rule the house.