D.P.
It's normal at that age. Try to reassure your husband that it's nothing personal. 6 more months and your son might only want daddy and not you. In the meantime, I'd schedule full mornings or afternoons of shopping trips to do SOLO when your husband is home. Don't try to sneak out when your son isn't looking (that's not fair to him). Simply say, "Mommy has some errands to do. Have fun with Daddy when I'm gone. I love you - see you soon!" and then LEAVE. NO LINGERING. He will scream and sob until you are out of sight and maybe longer - but Daddy can handle it and your son will be fine. Be sure to stay gone long enough for him to recover and then enjoy himself during Daddy time. The time away will be good for you, too. :)