sounds like your dog is taking the baby as a treat, you need to socialize the baby and the dog more, i understand the baby is still young but with the dog not being your only baby its getting jelous over who owns you lol. i would try findin time to sit down with dog and baby and make sure the dog is told thats your baby. Dont turn it into a game though, but keep a very close eye on both of them and the reactions of the dog, you can easily tell when a dog is being aggravated. Hope this helps you a little, my dog use to act like that with my nephew so i tried having him around more so i could socialize my dog with a baby.