Welcome to the Healing Well Wrapped Club! I know how bad the shoulder pain can be. The night nurse at the hospital clued me in on the importance of walking post op, and I soon found that the more I walked, the less my shoulder hurt, and visa versa. Give walking a try. The more you can walk, the better (within reason, of course).
The shoulder pain is from a combination of residual gas (they pump you full of air so they can see what they're doing in there during surgery) and irritation to the diaphragm. Give the walking a try. If you're like most people, it'll help. That pain fades over time, but really, it can nag you for quite a while at a much lower pain level. Walk, walk, walk...you'll be glad you did.
Swallowing is dicey for quite a while, and at 6 days out, you're at the worst part of the healing process. My surgeon warned me that during the first two weeks my wrap would become increasingly swollen, and my swallowing would get worse before it got better. Peak swelling hits anywhere from 2 to 3 weeks, then gradually recedes and things begin to improve.
If you're having trouble, try backing off on your eating...either go back to liquids, or be absolutely sure you're chew, chew, chewing your food until it's a complete liquid/creamy consistency.
Here's a link to my early recovery journal. It might give you some information that is helpful:
I suggest you start a new thread on the main page. Introduce yourself, and you can even copy and paste your post below. People will be able to find your questions more easily. Be sure to write a topic title...maybe Post Nissen Questions would be a good one. Whatever you'd like to call it. Here's the link to the main page: GERD - Heartburn
Hang in there! It gets better...