7 years ago started suffering from fatigue and brainfog, one of the tests i had was chest ct. now undergoing tests for lung cancer. could the start of lung cancer have been the symptoms of 7 years ago even though ct was unremarkable? thank you?

This seems very unlikely though many cancers can stay microscopic and asymptomatic for many years. Once you have a confirmed diagnosis you should discuss this further with your doctor.

There are blood biomarkers available to diagnose cancer. A detailed Neurologic examination is recommended. Maintain a healthy weight, BP and exercise as tolerated.