Hi there -:) welcome. And it's got to be scary! The tables have turned and instead of being overweight your having trouble keeping weight on. Life can be weird sometimes. Sugar for anyone is not a good thing either is high fat, but then the problem remains what to do to gain weight - for me the response is to eat healthfully - whatever is an average sized meal - and have it as frequently as you can. Then try supplementing it with shakes that you make. There are plenty of protein shake mixes out there that use alternative sugars - which affect your glycemic index minimally (stevia is usually the base - try to avoid the ones with fake sugars - aspartame and white sugars) you can add a bit of fruit, then a milk of some sort (almond or whatever) that is low fat and maybe a small scoop of peanut butter, unsweetened cocoa etc...have these in between meals. Try alternative pastas - maybe kamut, quinoa, not white flour pastas - they may be more tolerable. I gather your problem is not eating but the amount and type of foods. So eat all the time but eat stuff that will not set off the dumping. Ultimately frequent healthful meals - if our not a Veg head (I am!), then maybe lean chicken, fish, in a wrap and a smoothie chaser - vegetable pasta (preferably non white flour pasta), with a bit of chicken - and a smoothie chaser. Carry it with you if you can and drink constantly that way your not overloading your system with a big meal but rather feeding yourself calories (healthful) all the time. hopefully this helps!