What Causes Recurring Cold Along With Muscle Pain In Body?

Hi my daughter is 27, hasn t been feeling great since the new year, more cold issues than anything. This am she texted me and said that she was on her way to the dr. She was feeling awful. Muscle pain thru her entire body, when she coughs her head pounds. They did a flu test that was negative and said she had acute bronchitis, gave her antibiotics and to continue taking whatever headache mess she had been taking Tonight she is still in pain and is scared that there is another issue, I actually agree she doesn t sound bad but feels awful Thoughts?