I have heard oatmeal helps a lot. Plus it's super-healthy and fills you up. Lots of water. There is also something called Mother's Nursing Tea; you can get online or at the health food store. It has all the stuff (fenugreek, milk thistle, etc.) that helps with milk production.

If you can't handle a lot of food, then snack often and well. Anything that you can handle is good right now. Bananas, papaya, any vegetables, any way you can get them. Nuts for protein if you like them. Avocados have excellent monounsaturated fats in them (in fact, it's a great first food for babies, imo). Lots of water ;-)

Sunflower seeds, while high in fat, are very healthy and have HUGE amounts of calories. 1/3 cup has 340 calories, more than half of what you need for breastfeeding supplementation.

Do what you can. It's hard, and especially hard when all those hormones are flooding your system and you feel like you'll never be rested again. Hang in there.

BTW, have you had your gall bladder checked? Especially if you feel sick after a high-fat meal. . .