I've had the same problems for quite a while now. Looking up information on line there's a couple things that it might be related to. One is leaky gut syndrome, which many doctors view in a very skeptical manner. Basically, acid controlling medication has an adverse effect on your body if you take it for too long. It starts to seriously alter the way your digestive system functions. I was on acid control medication for years, and I'm just now starting to realize I need to watch what I eat and not just pop a pill and expect it to take care of everything.
Basically my symptoms: pain and bloating under the left side of the ribcage, dizziness, gas and abdominal pain after eating certain foods (especially dairy), anxiety, lack of energy, shallow heartbeat.
It got to the point where I was shaky after every meal. So I looked up some information, changed my diet to the strict diet suggested and it helped a lot. Things to know: if you're having issues with your digestive system raw garlic is basically the best natural antibiotic available. Food to stay away from: Anything dairy, anything with gluten (breads, pastas, etc.), processed meat (sausage, salami, bologna, etc.), corn, mushrooms, potatos, anything with a lot of starch, alcohol, smoke of any kind, caffeine, fructose sugar (sodas, fruit juice, cookies, cakes, anything dessert really)...
Things to eat: lots and lots of raw vegetables and fruits. Turkey seems to be fine for me, so I generally get my protein that way. Also raw onion is a great natural antibiotic as well.
Taking vitamin B12 pills helps a lot to get your energy back since your body may not be producing it correctly. Most importantly, write down when you aren't feeling good and what you did beforehand. If food is what made you feel bad, then make sure you write down what you eat and stay away from that food until you start feeling better. Your digestive system can form allergies to foods when it's in a state of disrepair and every time you eat that food until your body is feeling better it will automatically fight it off. Hopefully this helps, it's helped me a lot so far. Wanted to share with you in the hope that you start feeling better as well.