Nausea could be the beginning of gastroparesis. This is when you get neuropathy of the nerves running the stomach.

It can also be from a poor lining, or from an H. pylori infection.

Essential fatty acids maintain the lining of the stomach.
This is Flax oil, evening primrose and fish oil.

So to start, I'd concentrate on them. There are foods now with them... Smart Balance Peanut Butter, Smart Balance spread (butter substitute) and Omega-3 Eggs, Smart Balance Mayo.

Start with that and you may avoid taking capsules.

For nausea I like ginger extract in capsule form. YOu take it with a glass of water and remain upright (it may reflux if you lie down). This is very inexpensive and available in most health food stores. If you take it 3 times a day for a week, and your nausea improves, then you can eat better and get those EFAs into you for repair.

I suspect you are low in B12, and if so it will add to neuropathy woes ... Long term use of acid blocking drugs block your body's ability to absorb B12.(these drugs also block folic acid, calcium, zinc and magnesium, and iron). And yes, you can be low and NOT anemic. The anemia only comes with very low levels over alot of time.
I'd start on 1mg of methylcobalamin ASAP and take it every day forever. The methyl is activated to work in your body right away, the common cyanocobalamin is synthetic and requires 4 steps to be used~~ and these may fail.

This is an example of 1mg:
http://www.iherb.com/ProductDetails....1&pid=129&at=0

this is 5mg:
http://www.iherb.com/ProductDetails....1&pid=117&at=0

The 5mg once a day for 2-3 months would work faster..if speed is important to you. This supplement is not commonly found in local stores.
One should take it on an empty stomach once a day. Food interferes with absorption.

Once your nausea settles down, then you can add other things.
I'd look at whey protein shakes with fruit (supply potassium) to improve lean muscle mass which you are losing from not eating. Whey protein is predigested and quickly utilized. (if you have some digestive problem, it usually bypasses that).
Ensure is okay, but less concentrated in this regard.

We have a member with gastroparesis on our Peripheral Neuropathy board. She can help if you need her input if this turns out to be your problem. Her user ID is kmeb.

Males have another problem with weight loss/malnutrition. The blood proteins that carry testosterone throughout the body are made from the protein you eat. When males become depleted in protein due to illness/surgery, or poor food intake, these proteins cannot do their job, and
males then suffer from LOW testosterone. Besides the sexual dysfunction, there is a loss of
muscle mass, and generalized fatigue and loss of strength and vitality.