9 month old puppy aggression

Question
I have a 9 month old neutered lab mix, who we adopted when he was 3 months old. I was the main person in the household who house trained him, as well as basic commands. He used to listen to me.
I am currently 7 months pregnant, and am at the end of my patience with him. He used to listen when told no, or reprimanded, but now he instead will bark and snap at me in response. He continues to jump on my roommate, but she doesn't yell loud or reprimand him half the time, so he will continue to do it until I step in and tell him NO, and then he will snap and bark at me.
i am about to have a newborn in the household, and I cannot have him acting like this. I have tried to give him treats when he is in a calm state, and acting very nice. But, it has shown no improvement. Could it be that he senses my pregnancy and feels threatened by it? I am having a boy, but I don't know if that has anything to do with it.
I have also asked for consultations with dog behaviorists as well to help me with him.

Answer
Dogs do, of course, detect pheromones of pregnancy.  And I have had clients whose dogs became aggressive during the owner's pregnancy.  I think, however, that this dog is responding to the sort of training and "reprimand" being done.  You, also, are experiencing great changes in your behavior and emotions as you anticipate the birth of your baby.  This is an extremely stressful time in a young woman's life and often there are changes in a woman's behavior and these can include fear (of the unknown and responsibility), anxiety and even depression (hormonal), along with the joy and anticipation.  These are NORMAL but your growing lack of patience toward this young dog (who is an adolescent now with tons of energy, and a breed mix with a great deal of boisterous behavior -- which is what you describe "jump on my roommate") is most likely causing him great confusion.  Don't beat yourself up over this!  You've got a plate full.

I think you need to do two things: find a REAL behaviorist from the following sites:
http://certifiedanimalbehaviorist.com/page6.html
http://www.arkanimals.com/ark/dg_expert_referrals.html
http://www.animalbehavior.org/ABSAppliedBehavior/caab-directory

Stay away from dog trainers, you need real expertise here.  

Second: change your method of dealing with his boisterous behavior.  The "snapping" you describe might not be active aggression (I can't see anything from here) but the VERY LAST thing you want to do is repeat any of your own behaviors that provoke his barking and "snapping".  The word "no" needs to be eliminated from your vocabulary (this will greatly benefit your baby, too!)  Offering a dog treats when he's "calm" isn't a consistent method since you have to know what the dog is THINKING when the treat is offered: you really don't know what you're rewarding and neither does he.  This is a lot of "free" reward.  Rewards need to be associated with the performance of behaviors you have taught him using ONLY positive reinforcement:  "sit", "down", "come", "off", "bring it", etc.  Once the dog understands what you want from him and VOLUNTARILY performs for reward, his hysteria should begin to diminish.  You can learn a great deal about this sort of training from Dr. Ian Dunbar's site: DogStarDaily.com.

Additionally, there is some work you need to do and these are articles that address those:
http://www.dogstardaily.com/training/handling-and-gentling
http://www.dogstardaily.com/training/excessive-barking
http://www.dogstardaily.com/training/jazz-and-settle-down
http://www.dogstardaily.com/training/teaching-bite-inhibition
http://www.youtube.com/watch?v=ApIJV8oGphg&feature=related

As you await your appointment with the behaviorist and study the material offered above, put a house tab on this dog (leash with handle cut off) when you are at home.  If the dog jumps up, pick up the leash, turn your back on the dog, turn back to him, signal him to "sit", reward it, walk away.  Every time (you have to be consistent) the dog jumps up, this is what you must do.  Don't yell or get angry, this is only making the dog more anxious and fearful: almost all aggression is fear based.  When a young dog like this begins to fail, it's always the training (unless there's a biologic cause) and not everyone can be expected to know how to train a dog properly.  So self blame isn't an option here, this is your opportunity to learn and it will be of great benefit as you raise your child (toddlers can be quite demanding lol).

If the dog barks at you even after you've done the work found in the excessive barking article, leave the room.  Put a closed door between you and the dog for ten seconds.  Do this until the dog has stopped barking, then ask for "sit" and reward.  If the dog NEVER gets to the emotional state that causes "snapping", he won't learn any more about how to use aggression to control you, and this might not be out and out aggression (since I can't see it, as I said earlier).  Your roommate can act as you do if s/he chooses, but this is ultimately your dog.  The dog needs to be prepared for the infant to come.  Your behaviorist will direct you.  Right now, put him on Nothing In Life Is Free (NILIF) which simply asks the dog to "sit" before being fed, taken in/out, interacted with in any way (including play and being petted).  Can't hurt him, can help him to feel more secure.  Change the command words from the standard ones (sit, down, etc.) as you re-teach him behaviors.  Use unique words.  Don't hesitate to ask followup question if needed.