My Son Who Is 18 Years Recently Had C-Diff Caused

My son who is 18 years recently had C-Diff caused from antibiotics...he is recovering slowly from the C-Diff but is now vomiting. He vomits with no warning, nausea or ill feelings after the fact. We have been through many blood tests and are set to go to a gastroenteritis at the end of this month...we are quite concerned. The C- Diff diagnosis was in November and he is still unwell. Any clue?