sounds very scary...as a suggestion, keep a journal of what you're eating, how much, and what happens exactly, for how long, and how it goes away. It could be a food allergy? And keeping track of what you eat is the best way to determine what you may be allergic to. Food allergies can develop over time, so even if you weren't allergic to anything before, you may be now. If it's something like soy, it could be in nearly everything you eat, which is why you feel miserable all the time, Or, if you're allergic to wheat, like Celiac's Disease, you could be responding this way nearly everytime as well. Get to a doctor before you a have a more serious reaction next time.
Food allergies can definitely cause your heart rate to increase after eating something that you are allergic to. You may want to check out my journal on allergies and how to help find out what you are allergic to... I include food allergies as well: