....to read how upset your pup gets.
I don't have a lot of knowledge on the subject and don't know how long you have owned your dog.... am wondering if it is fear of abandonment (if he was from a shelter etc.)
I did read that sometimes if the owner leaves the dog alone for, say, ten minutes the first time; then next time, say, fifteen, then half an hour until the break is for 90 minutes, it can help
As I am new here I don't know if you have already tried this
ps My dog is 18 months.... I do remember taking her with me when I went out in the car to the store, and then only took her every second trip....
sort of so she knew where I was going (does that make sense)? She knows now that sometimes she can come with me/us and sometimes has to stay home.