I understand. I was at a healthy 145 and had a tragedy. I couldn't eat and wasted away to 115. I looked terrible and felt terrible. My small stomach simply wasn't hungry and if I COULD eat I couldn't get enough calories in to maintain weight.
It took a very short time to lose that 30 lbs and longer to put it back on. I can tell you what I did if it might help.
I stopped drinking coffee (appetite suppressant);
I started eating fried eggs for breakfast, lunch and dinner. It was the only food I could really eat and keep down and it had protein. I used plenty of butter - my skin got dry and my doc said butter fat and cream would help;
I drank whole milk, sipped it, and half and half sometimes;
I ate whatever cheese I wanted, frequently
I stopped exercising;
I drank a little red wine (doctor recommended, yes it helped gain weight, but I wouldn't do THAT again. Led to enjoying too much and had to just stop later.)
I started making SOUP. Rich soup, like baked potato soup and the like. It was chock full of healthy calories. It was the only way to get it down.
Now you may not be in the same boat, so take or leave what may help you. I hope this helps some. I had nobody to guide me on this, I did what felt right, followed my cravings, and did ask my doc at one point. He suggested a couple of these. I discovered the others.
I hope you find what helps you. I do know how distressing it is and how it feels. I wouldn't go back to being that skinny again. Even though being fat for so long did make it kind of nice to be so low, it was unhealthy. I'm at 145 or so and maintained that for last couple years. It's the right weight for me
Take care and I hope others help on this. It's a tough one.