Whenever i eat or drink something i get nauseous and feel like vomiting it up. i'm always weak and tired?

First, get diagnosis: Normal, healthy people do not have constant tiredness, without a good reason. One's primary care doctor can follow along and look for reasons for fatigue, such as anemia, infection, mental illness, auto-immune disease, thyroid problems, cancer, insomnia, etc... Various tests may be needed, depending on one's whole story, and sequence of symptoms.

Need assessment: This constellation of symptoms can't be diagnosed with the available information. A medical assessment to include full history, laboratory evaluation and physical examination would be needed.