I suffer from the same things that you mention but usually before and after I run (it's much worse the morning of a race). I am a biking newbie and don't ride for too long or too far yet so I have no idea if this will also be the case for me when biking.

I read something in Runner's World and online that might be informative. I have posted the link to the runner's world article and copied a couple of sections I found interesting (and you might as well). While this seems to be written regarding issues with nausea (and even undigested foods), I find that I have something that happens with my stomach and this causes me to spend a lot of time in the bathroom/porta potties before or after a run.
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http://www.runnersworld.com/article/...-1-3-2,00.html
Solution: Settle your stomach and mind.
Eat a light meal that is low in fat, protein, and fiber at least 2 hours before a race or hard workout. Also, practice relaxation techniques to reduce stress. If throwing up has become a conditioned response to hard races or a particular workout, give yourself a reward every time you finish a race or workout without getting sick. And always have positive mental images to recall if you're on the verge of becoming sick. Recall a cold, clear mountain stream, or something else refreshing.


Problem: Slow digestion
When we exercise, blood is shunted away from the stomach in order to supply the muscles and skin. As a result, your digestion slows. So, for example, if the sports drink you use during competition is too concentrated, it will not be absorbed and will either sit in your stomach or be expelled.

Solution: Reach for less-concentrated drinks.
Make sure your sports drink is at most 5 to 6 percent carbohydrate, and drink it on your long training runs. If you know a race is going to be offering a certain sports drink, practice with it beforehand. If you find that the carbohydrate concentration is too high for you, try drinking half water and half sports drink at each fluid station.

Problem: Anxiety
When we become nervous before a race, our sympathetic nervous system is triggered. This fight-or-flight mechanism is what prepares us for action. At the same time, the parasympathetic system, which directs digestion, is slowed. The bottom line: If your anxiety is too great, the undigested food in your stomach may want out.
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