Two possibilities come to mind:
As MMM mentioned, one possibility is IBS. If you're also experiencing loose, foul-smelling stools, and uncomfortable cramping, this is IBS. The reason this stings the anal region is because the intestinal lining of the small intestine is compromised, and increased peristalsis moves undigested food and enzymes too quickly through the GI tract. Enzymes that normally would be neutralized or absorbed reach the anus and burn. Food intolerance is what begins the pathology in the small intestine.
The other possibility, is if the stinging is the result of hemorrhoids, perhaps cracking and/or splitting. There are a couple of reasons for hemorrhoids, but one is candida -- which can also be related to food intolerance.
The dizzyness symptom you describe is troubling, but there is a condition known as "gluten-induced neuropathy" and "gluten ataxia"...also symptoms of food intolerance.
I suggest a food journal, and perhaps an elimination diet.