I'd agree with Cheesehead. My own intro to poly came in much a similar fashion, and it ended up in two months of constant fighting, anxiety, sorrow, etc. Only after my wife ended her relationship with her alternate and "came down" to my level was I able to quiet myself down and really try to wrap my head around things (with her help and support). If we had educated ourselves on the subject and improved our communication skills before exploring other relationships, I think we could have navigated poly without all the hurt and heartbreak.
Try to think about whether poly would be good for you and your husband's relationship first, and approach the issue from that perspective. From my own experience, and from reading a lot of other people's stories, it seems that if one party in a monogamous relationship proposes poly IN ORDER TO get involved with a specific person, that this causes a lot of stress in the relationship and a lot of hurt feelings. (Of course, you do want to get involved with someone else, and you shouldn't deny nor feel guilty about those feelings)
One guideline is that the relationship opens up at the pace of the slowest person. Move too fast and you risk damaging the relationship.
Frequently, couples have to improve their communication skills a lot before they can even discuss the subject in a healthy way.
Kudos to taking the time to research this first before moving ahead. Plenty of people just jump right in without making sure their spouse is comfortable first and end up causing all sorts of problems with their relationship.