Hi C.,
I breast fed my daughter too - I noticed when I ate soy products she was extremely fussy. I cut out soy cheese and that helped, and then I forgot and ate a soy pudding - and she had a terrible episode! Some babies are sensitive to things we eat - most common baby sensitivities are dairy, soy, gluten (wheat and all types of bread products - crackers, cookies, pasta, etc).
Try elilminating dairy and soy first, and see how your little guy does. Often, their little systems just need some time to mature. I also found I couldn't eat anything "gassy" like broccoli at first. I can't remember when I was able to add it back in, but my daughter is now 2 1/2 and she has almost no food sensitivities, and has been healthy as a horse! I like to think it's the breastfeeding...
Good luck to you - I see you have had lots of input on this issue - keep us all posted. If you would like to cut out some foods and need some tips on what else to eat, feel free to e-mail.
Warmly,
E.