DG sorry to hear you are feeling so sick, I can't help with the Zofran but on the constipation issue Metamucil can have opposite effect if you get dehydrated, something I found out the hard way.

I suffer terribly during pregnancy and the pharmacist recommended Lac-Dol which I've been taking on and off since 6 weeks and it works relatively quickly. It's a liquid which you can mix in juice or water to mask taste.