Anyone help me - Cooper is 4 months old, we have had him for a month now and he bites all the time...our hands and wrists are very sore - he has a selection of different texture toys and chewy tastes to eat which last a day, but before we can stick something into his mouth, he is biting us - I am sure it is excitement....we have tried using a stern voice for him to stop and I am hessitant to smack his nose....any advice please