I also have had this problem for a few years now. I went to a GI doc and did all the test and everything came back normal and healthy. Obviously I stopped going because he couldn't help, told me it was probably just stress. Well 3 years later it still happens with some months being worse than others. I eat very small amounts now because I can't hold anything down. I found that chewing longer helps with the undigested chunks if that helps. I have been doing some of my own research now and 1 thing I found is that it could be due to lack of acid in the stomach. I burp a lot so I thought it was acid reflux but it looks like it just might be the opposite. There's not enough acid to break down the food and it comes back up almost exactly how it went down. They say vinegar or lemon juice everyday can help. I am trying that now. There is also a pill but I'm going to try the home remedies 1st. If it works I'll pass it along.