There are several things that can contribute to a problem like yours:

- exercise induced peristalsis (increased contractions of the GI tract as your gut tries to empty itself during times of physical stress). Once the gut is empty, the blood is shunted toward the heart, lungs and working muscles.
- excessive fluid intake, especially if you are gulping large amounts at infrequent intervals. Sip frequently, never guzzle.
- excessively concentrated electrolyte/sugar solutions. These can temporarily pull fluid into the gut to dilute the high concentrations. Most sports drinks or electrolyte mixes can be diluted 50:50 with water and remain effective.
- irritable GI tract, stress induced irritable bowel.
- high volume/high bulk diet at inappropriate times. Try to stick to nutrient dense but low residue foods for the meal before and nutrition during the ride. Don't go crazy the other way either, you don't want constipation just a lower load on your gut.

The sports nutrition industry has us so afraid of "bonking" that many people go overboard thinking they have to load up on carbs and electrolytes. Yes, you need fuel and appropriate electrolyte concentrations and balance, but more is not better. I'm also an advocate of real food rather than sports gels, candies, blocks and drinks/drink additives.

My recommendations (try these on a training ride, never make big changes on the day of a major event):

- Stick to real food like granola bars or oatmeal raisin cookies which will supply both carbs and electrolytes with only moderate amounts of fiber.
- Refuel with small snacks of 100-200 kCal not mini-meals of 500+ kCal.
- If you think you need additional electrolytes, dilute your sports/electrolyte drink by half and sip small amounts frequently.
- Make your pre-ride meal small and nutritionally dense with limited amounts of fiber. Avoid dairy, except for yogurt, pre-ride.
- Avoid concentrated sports gels, candies and the like.
- Don't overdo fresh fruit like oranges, apples, etc. and don't drink more than a few ounces of fruit juice.
- Limit the volume you are consuming to what you actually need.
- Learn the difference between muscle fatigue, dehydration and actual hypoglycemia (bonking). Too many people instantly assume that any decrease in performance or feeling bad is the result of low blood sugar when this is often not the case.