My dog won't stop barking ever?

He is a West Highland White Terrier, one year old. I had my friend over today and he barked the whole time. My friend left. Barking. My mom came home. Barking. I brought him downstairs and he ran around, barking and peeing. My sister and her friends came downstairs and he started barking. I tried to keep him confined, but he barked more. I am holding him right now and he is whining and barking. He is well fed and just went to the bathroom. I feel like I'm about to cry because he just. Won't. Stop.