My Daughter Is 7 Months Old, Within The Past Month

My daughter is 7 months old, within the past month she had phenomena got put on antibiotics then got better, a week after finishing antibiotics she's sick again all the common cold symptoms, took her to get checked out Sunday the did chest x Rays couldn't find anything and said they expect her to be better by Wednesday which is tomorrow but she's worse today and now she has a constant cough and cries in pain every time. Are they missing something? What can I do she's so little?