Hi, I can sympathize with your situation. I have been down this road. But I will tell you it was OUR fault our dog bit, in the respect of training or lack of. You and your son did nothing wrong. Babies will be babies and dogs will be dogs. I know from experience that the dog views the baby as lower than him. You will need to be very watchful(I Know that is hard with an 18 mos old baby, I have twins, and had 2 dogs for 8 years b4 the babies came). I made sure my kids had a safe area, the dogs were allowed to enter but were trained that they had their area where they could have there space without being bothered or tugged on by the children. they would pull on them sometimes, and growl..but were told to leave and go to their space, where they could sleep or whatever, in peace. The problem came with our 3rd dog. We got her from a shelter and didn't have any formal training(Our big mistake) and she had issues, I guess when we got her, from the beginning if you stood over her, while sleeping, would growl. As time went on, my son who was about 9 at the time, would tease her at times, put her in headlocks...but would love her too..and one day she was sleeping and he went over to her, and her lack of trusting him, she got up and lunged at him and bit part of his lower lip. Alot of people did and will tell you to put the dog down. But that is NOT the right thing to do..it is our responsibility to train our dogs to give them discipline(not harsh) to show them you are the leader, including your baby. You must start now..to teach your son to not disturb a sleeping dog, as that startles the dog. Try to read some books or go back to a trainer, who can advise you the best way to handle this. Even at 18mos old you have to show the dogs who is leader..the dogs place is at the bottom of the totem pole and they are really much happier there. We have a golden now...she has a pushy personality, but everyday we do down/stays.make her do something before she plays, gets love and affection..we love her to death ..and it is hard NOT to just love her and love her..but it has to be earned. Every day you should be implementing leadership. As your son grows older have him participate in training(training is a lifetime job for your dog to establish their place), help him care for the dog..with feeding, grooming..to show the dog he is his caretaker and boss. Never with harshness, which puts fear in the dog, which put them on defense and will bite. good luck, don't give up on your dog..he deserves a good life, just go forward with caution and training, as hard as it is, keep a watchful eye, try to keep your baby and the dog seperated at times when you can't watch or when the dog is sleeping.. Contact a trainer, a few sessions will get you started establishing your family as the leader.