I'm 16 yrs old and ive had serious nausea and vomiting for about 2 weeks. Its been difficult sleeping too. Would I be prescribed codeine.

Probably not. One's primary care doctor can evaluate to see where the nausea and vomiting might be coming from. Many, many conditions can cause nausea and vomiting. Meanwhile, one can get a calendar and write down his story, from day 1 when things started happening. Include details on what actually happens, when it happens, what helps remove symptoms, what worsens symptoms, any food relationships, for the Dr.