Sometimes going from 0-100 can cause these kind of problems. You could try a more gradual introduction to see where your limit is.
Indeed
Have you investigated your stomach acidity?
No, I had moments, especially in 2013 when POTS peaked, that food felt like a brick sitting in stomach doing nothing. I expect it to be on the lower side.
The first symptom arose during breast feeding at age 2 days. Cardiac Pulse faded until it was gone. They gave me smaller portions and it didn't happen again.
My guess: I think that neural networks were overloaded. I have this problem to this day, portion size puts a load on my brain and on some systemic network. Digestion in stomach can affect my respiratory rate for example. It feels like the body has to work harder, as in, providing/directing power but at the cost of other functions. That's why the cardiac pulse probably went weaker when I were a baby.
My uncle, as a baby, had a reaction to porridge (gut). Had to be taken to the intensive care unit.
Then you have POIS. Orgasm can make me feel weak (nervous system?). Add that digestive effect on top of it when eating during POIS mode and it will be even more difficult to digest stuff. There is also a local contact reaction going on between food and stomach for some type of foods, but I think that is immune related.
Large meal size can also be more demanding (on my neural networks?) when relatively powerfull peristaltic movement of gut is necessary.