Hi K.,
One question: Is your son acting better on formula?
If not, why not continue breastfeeding, but try a food elimination diet if you don't want to quit breastfeeding?
My son had reflux (until around 10 months) and still has food allergies (15 months now). We did the allergy elimination diet (really hard, but easier with supportive husband, friends, and family) around 4 months and began reintroducing foods around 6 months after everything was out of his system. I never tried formula, as the blood in his poop disappeared after food elimination. By the time we reintroduced foods to my diet, he didn't react to anything from my breastmilk anymore, so I am able to eat what I want again. The gastrointestinal doc said that their little stomachs aren't fully developed until 6-8 months, but once that happens, the proteins they are sensitive to can't get out into their bloodstream anymore. We found a really good naturopath to help us find herbs and supplements (probiotics, magnesium) strengthen young one's digestive tract, too.
I personally found the support and information from my local La Leche League group to be very helpful. Please contact them if you wish to continue breastfeeding. They can help you with supply issues if you are facing that, now, and can give you assistance with food allergy issues.
On the food elimination front: there is Rice Dream ice cream (pretty good) and brown rice bread, and you CAN have chocolate if you read labels carefully and stick to dark chocolate found in health stores.
Please email me if you wish to talk further. My son is now fully allergic to eggs and dairy (we carry an epi pen and benedryl in the diaper bag), and he refused to start solid food until around 10 months (a common thing for food allergic kiddos).
Good luck and best wishes to you.
H.