chelle,
I too have gastroparesis, a nightmare, but I have a wonderful doctor who is constantly helping me work with medications to keep me feeling as good as possible. I too was benefiting tremendously from Zelnorm, and i am missing it. Some other meds you might want to ask your doctor about if you haven't tried them already:
-Domperidone
-Marinol
-Scopolamine (yes, slows down the stomach but if your condition is bad enough anyways, the anti nausea effect is really strong and it can be worth it)
-Anzement ("dolasetron")
-Erythromycin (sp?) used on and off to promote motility since it becomes ineffective after a couple weeks

See what your doctor says, these are just some of the ones that are a bit outside the normal anti nausea arena that might be worth a shot depending on your specific profile. Quick question, did your GP start after your children were born? Just curious, mine did.

-Best of luck, always remember there is hope of feeling better someday soon.