Is he vomiting and have diarreha?Make sure he is hydrated with pedialite and continue to breast feed you perhaps can leave any solid food till the symptoms cease.
You say "I have a 7 month baby and has the stomach flu." Do you mean you have the flu or the baby has the flu? If the latter, go with the advice from margy. If the former, feed the baby as usual, keeping yourself as hydrated as possible. (Stomach flu doesn't transmit in breast milk.)