My ME feels a lot like a chronic infection, and parts of my immune system are probably (mal)functioning as though it were responding to an infection, but my guess is that I don't have an active infection and that the problem is that part of the immune system is simply locked into an abnormal state. Some people here have reported a reduction in symptoms from treatments for infections, but such benefits seem to be rare. I think we all wish that ME/CFS was just an infectious agent, because that would mean it could be identified and treated. You can try to get tests to show whether you have an active infection, but don't be too surprised if none show up.
As for vitamins and herbal remedies, we all seem to respond differently to them; that's just part of ME/CFS. Some people report reductions of symptoms from something, and others report worsening of symptoms from the same thing. One thing I recommend is keeping a journal of food (and supplements and treatments), activity and symptoms. That way you can look back to verify whether something has a repeatable effect. If you identify something, you can then try to figure out what it's doing, and what other substances might have similar effects. For example, I learned that herbs and spices that are peroxynitrite scavengers make my symptoms worse. B2 and B3 make my symptoms worse. My observations of what makes me feel worse, and experiments to identify the active compounds, has led me to avoid quite a few foods, which thus reduces the days when I feel worse.
Getting prescriptions for ME/CFS symptoms are kind of pointless, because no one knows what is malfunctioning in our bodies, so how can anyone know what will fix that? The prescriptions based on symptoms (fatigue, etc) are for people with other disorders. You can probably make as good guesses for things to try as any professional doctor.