I get this way too. When old favorite ways to distract from intrusive thoughts no longer work the way they once did, what helps me is to find something new. The novelty excites my brain and gives me something more positive to become obsessed with, and unhappy obsessions/ruminations fade away. Maybe it would help to try something new with your dog as well, even if it's just going for a walk in a new place, or teaching him a new trick or giving him a new toy. You can experience this novelty together and feel closer again.