Anxious Pom ...

Hello. We got Archer, our lovely 2 year old Throwback Pomeranian just over a week ago. He has settled in lovely but has developed a very strong attachment to me. He is fine when my partner leaves the room or goes out, but if I do, he either follows me to whichever room I have gone to, or is very restless, walking back and forth from the door until I return (even when my partner is still home). We haven't even attempted to leave him completely by himself yet and would love to get any advice on how we can help him overcome his anxiousness as there will be times in the future where I do need to leave him at home for short periods of time.
Thanks, Jessica.