Please help 🙁

I’m pet sitting a 1-2yo dauchand and he’s a very sweet boy but he is non stop barking 🙁 I know dogs bark, it’s not like that. I throw his toy for like 45 minutes and as soon as I stop he keeps hysterically barking- he will not stop, he either barks at me or then runs to the windows and barks outside at nothing and whining. He will bark at the window NON STOP like did it for an hour when I was trying to do my work. I had him out in their yard throwing his toy and he just stopped and stood at the drive away barking for like 30 minutes straight before I tried to distract him and let him in. He won’t let me go to the bathroom, and I took him on an hour and half walk and he got back home and just starts barking again. I feel horrible. I don’t know what to do because he’s I’ll play with him but as soon as I try to use the bathroom, do a little homework, anything- he will bark. I just don’t know how to help him 🙁