For the last 3 months Harvey has had someone with him all the time, this morning I went shopping, OH was at work and son was in bed asleep with his bedroom door shut, when I came in from shopping son said to me Harvey had woken him, he was constantly barking and howling, son called to him and he was then fine, after putting shopping away, both son and I went out, when I came back 20 minutes I could hear him howling down by where I had parked my car, son came in so I said to him lets both go outside and see if he barks and howls within a minute he was barking and howling, he has never done this before, so it has made me anxious about leaving him alone, when I do go out I make sure at least 1 cat is with him, the lamps are on and he has the TV left on, he is not left in 1 room he has the run of the house, any suggestions would be helpful.