Ultrasound showed diffusely heterogenous liver texture. google results are showing possible diffusely infiltrative tumor as possible cause. doctor ordered mri follow up but said it is not cancer. how can my doctor be so sure? worried sick?

It is not feasible to provide a meaningful opinion without taking additional history, physical examination and may be some tests. It would be prudent to see your doctor and discuss if you may be depressed. Counter-intuitive as it may seem, exercise may help. Start with low intensity exercise such as walking and gradually increase the intensity as tolerated. Drink more water. Wish you good health!