What Causes Vomiting And Decreased Appetite While On Treatment For Bronchiolitis?

My 5 month old was diagnosed with bronchiolitis and infiltrate around his heart. He is on an antibiotic and breathing treatments right but he still wheezing after his treatment and the coughing seems worse. His breathing does seem slightly labored. His appetite has decreased and when he does eat he is projectile vomiting, no signs of dehydration though. Should I be considered? He has been to the ER twice in 4 days for this, does he need to go back?