Early satiety is the hallmark sign of gastroparesis. You really might consider talking to your GI doctor about a simple test to check for gastroparesis (eating some contrast laced scrambled eggs and lay down for a couple hours while the nuclear scanner images and track the food to see how long it takes to empty the stomach).

Even if you have it, there is not any good medication options in the US. Most of treatment is life-style changes. So it wouldn't hurt to try some of the changes even without a Dx just to see if it helps. Eating small meals more frequently is top of the list. It also helps to get up and walk after eating to help move food along. This alleviates the full feeling and and discomfort/nausea that can come with it. If the stomach gets a little help emptying (with the walking) then you'll be able to eat more at other times.

Also stay away from hard to digest foods like raw fruits and veggies and nuts. Steaming veggies is the best way to go and fruit should be in moderation anyway due to the high fructose content.

If you have any nighttime symptoms, then raising the head of your bed helps to allow gravity move food out.

If you have gastroparesis, then this would explain why you can't eat much and also why you may not be absorbing nutrients (gastroparesis can impair absorption). May be worth checking this out.