Hmm, I was thinking along the lines of separation anxiety, but if you were both home then that theory goes out the window; unless you were both behind closed doors and he couldn't get to you. There will be a reason why he's doing what he's doing it's just a case of figuring out what it is So very frustrating
I know you've got pet insurance for him - contact the provider and see if they provide cover for a behaviourist then ask your vet for a referral