My dog is becoming very violent whilst he is barking..?

me and my family have had countless dog trainers come to try and stop our dog from barking. he never used to be agressive before but now whils he is barking he becomes defensive and occasionaly bites me not my other family members. i am the younges and i often shout at him because he is barking so loud. one of the dog trainers said the cause of his barking was because he was stressed and we followed all her instructions but they never worked and he's becoming more and more violent. i really am at loss as to what to do i need help before he gives someone a serious injury. he's a cairn terrier (a small dog) and he's about threee years...