Rubylizard, your head is afraid of your body. There's a connection there! You've heard of cancer victims visualizing little monsters to eat their cancers and how that can work; your mind has all of the influence there is over your body when there's nothing physically wrong with your body. Your body isn't a separate entity that ultijmately somone (therapist) outside is going to make obey; only your own head can do that. Your head "invented" the symptom in the first place. Have you tried dialoging with your body, seeing what it "wants" or is getting from the phobia? Is there a progression of what makes you naseous so you could "practice" on something that you probably can eat but which makes you not feel very well. I can differentiate in my body between when my nausea is going to make me sick and when it is eventually just going to go away.

I imagine you have regular "talk" therapists in town? Go to one and work with them on cobbling together a therapy you both would like to try with you. Therapists give suggestions on how to treat someone based on what has worked with their many clients with illnesses similar to yours in the past but it's possible they're not set in concrete how they're willing to treat you. You can talk to them about why you don't think their way will work for you and work hard to try it rather than just have your head reject it and when it does or doesn't work after a good trial on your part, then you and a therapist adjust the therapy, knowing more about what does and doesn't work by experience together instead of you coming in off the street, all control and quite sure nothing works and unwilling to get to know a therapist and try to work with them to get to know you better. Get out of your own way; you're not the first or last person with this symptom.