I'm thinking it could be nutritional as well.
I eat 2 hours before a ride - usually 2 eggs, a fruit smoothie (banana, handful of blueberries and one other fruit blended with almond milk) and then either make amaranth pancakes or oatmeal.
I always carry 2 water bottles. The first contains electrolytes, like Nunn - the other is water. If I'm riding more than an hour, I drink the electrolyte bottle first, then move on to water. I keep this rotation - one bottle electrolyte, one bottle water, for the duration of the ride.
I eat every 90 minutes or so - a banana, a granola bar, a homemade fruit roll-up, or on long rides, a powerbar type thing.
Post-ride, I probably eat eggs again, or fish if I have it handy. Gotta feed the muscles. I also eat fruits and legumes, and roasted veggies.

I hope you figure out the cause of this - bonking is NO FUN.