How long have you been working on this?
Has anything happened to make you think you won't keep making progress?
What sorts of feelings and reactions are you experiencing?
Do you have an idea of where it's all coming from... fear that she'll like something about him better than you, fear that she'll love him more, fear she'll get pregnant, etc?
Have you considered couples counseling with a poly friendly counselor (it's gotta be cheaper than moving!)?
Have you read the resources on dealing with jealousy at www.morethantwo.com?
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.