Don't be terrified, you've just had major surgery and are starting to heal.
It's unlikely the feeling you are having is reflux - most likely this is just your brain registering the post-op swelling and pain in this way.
What are you eating/drinking? A few days after your op you should only be on a liquid/very soft diet.
I've read that some people find sleeping in an easy chair easier just after there operation, so this might help get comfortable at night in the early stages of your recovery.
Hang in there, it does get better - I had my op almost 11 years ago and haven't regretted it for a moment.