I have been having severe post-meal crashing for several weeks and haven't been able to figure out what's going on. About 15 minutes or so after eating, my brain literally shuts down (I can't think at all) and my body feels so week that I have to lie down immediately. It takes at least 2 to 3 hours of resting to recover and feel "normal" again. I have been on a gluten, dairy and sugar-free diet for many years and avoid foods I'm allergic to. I also eat a high protein, low-carb diet. I've been on a rotation diet for many years, so I eat the same thing rotated every few days. It's been happening every day, so it doesn't seem to matter what I eat. Does anyone have an idea as to what might be causing this?