Personally I'd stop. Babies lack the enzyme to break down solid foods until they are about 6m old. I think she is telling you she can't handle it, it is most likely causing severe gas (causing pain) and perhaps nausea.
What are you giving, cereal?
Why did the pedi tell you to do this? Just curious. Regardless I'd stop and try again at 6m old.
HTH some, good luck.
Zoey