Welcome to Healing Well! You're definitely in the right place. I had the surgery in February 2009, and also suffered with asthma made worse by reflux. I had a small hiatus hernia, so you had me beat there!
As far as eating...
If your surgeon hasn't put you on a strict diet, then he means for you to use your good sense and select foods that will work for you. My surgeon gave me this rule of thumb--eat anything that you can chew to a liquid. I loved being on that diet, because I enjoy eating, and I wasn't looking forward to drinking my meals for an extended period of time.
You will feel full without eating very much--it's very natural. The diarrhea is also very normal with the surgery...you've had your GI tract revised, and your stomach isn't happy with you. You may get some "dumping" when food goes too quickly into the small intestine, and that's a major cause of diarrhea. There's no reason to worry about
it. As things heal and get straightened around, you'll get back to normal.
As Alcie said, you should stay away from bread (you can eat the crusty outside, or toast it, and you'll probably do just fine). No steaks for a while, either. My surgeon said that just because something is soft doesn't mean it will swallow easily. He said that you could get a bolus of mashed potato that causes you trouble, while something solid that is chewed carefully will be fine.
I like that my surgeon trusted me to make good and careful eating choices. Really, the world of food is
opened up for you, as long as you don't swallow anything that hasn't been chewed thoroughly. If it doesn't chew to a liquid, discreetly remove it from your mouth!
My surgeon's nurse suggested that I not talk while eating--the reason was twofold. First, you might forget yourself and swallow something you shouldn't, and also, it introduces a lot of air into your stomach.
Don't use straws, (all kinds of air gets put into your stomach), and don't drink carbonated beverages. You've probably heard all those things.)
I found that stew beef, potato, onion, and carrots cooked for hours in a slow cooker came out soft and delicious. I had figured on only eating the beef flavored veggies, and found the beef to be so soft that it was easily chewed to a liquid.
Soups cooked a long time so that veggies and meat are soft, work very well. Chicken chews to a liquid pretty easily. Crackers and crispy things are easier to chew to a liquid than softer things.
If you get bloated, try Gas-X. That works for many. The walking is key...it will help you get your strength back, and get rid of the gas they filled your abdomen with when you had the surgery. If you have shoulder pain, that's one of the reasons. Walking is the best thing.
As far as driving, it think it depends on your recovery. That's a good question for your surgeon. I've heard of people who went back to work after just two weeks, although I think that is not ideal if you have the option to take longer. One friend here--Joy--went back to teaching first graders after just two weeks. God bless her! That was definitely a challenge.
So the long and short of it...get nutrition by eating foods that are easily chewed to a liquid. Take small bites and chew, chew, chew. You'll not have any problems at all if you do that.
Your attitude is great, and that's more than half the battle!
Hang around here. There are many who have gone through the Nissen surgery and recovery, so we'll help as much as we can.
Take care and feel well!