I tried edamame once and it acted rather quickly as a laxative - trying not to be too disgusting here, I know people who love it, however... I only tried it that once and thinking I should not try it again, but I do love crunchy snacks :-)
Often when a body first encounters something it has trouble digesting it. I would suggest getting a small steamer bag of edamame and trying just a few. They are quite good for you, and it'd be good to get your body used to what they offer.
It's the same with a number of healthy food items - you have to wean your digestive system on them
Dianne, if the edamame you ate was crunchy, they were fried in some type of oil. It is more likely that your digestive problems were caused by the oil than the edamame! Do beans and legumes have laxative effects typically? I know they can cause gas!
Anyway, try to eat them lightly boiled in the pods. Find them in your freezer section either in the pods or hulled. Either way, they need to be blanched and then salted.