Can being lethargic and tired all the time be related to a brain tumor?

Overwhelmingly NO.: Confusion, dizziness, memory loss, slurred speech, loss of balance, weakness on one side of the body, seizures or blurred or double vision could signal a stroke or brain tumor, so always demand prompt medical action in those circumstances. Isolated headache is rarely caused by brain tumors. Your symptoms and age make a brain tumor very unlikely.