There are as many variations of polyamory as there are flavors of ice cream!
Not everyone is comfortable with practicing poly.
TALK to your husband. Explain your fears. Spend some time looking deep within yourself to find out where these insecruities are coming from.
Above all COMMUNICATE, COMMUNICATE, COMMUNICATE!
What I found most helpful when dealing with my own jealousies is a couple of the articles on http:///www.xeromag.com/franklin.html
more specifically this http://www.xeromag.com/fvpolyrefrigerator.html
Good luck to you. Really, it is ok if you discover you aren't meant to be polyamorous.