I feel fatigue and tiredness quite often, is it due to liver?

Many causes. These symptoms are probably the most common and the less helpful to guide to a diagnosis. The causes could be psychological (like depression, stress) or physical (infections, tumors, autoinmune diseases, or just a poor diet!). The systems that can produce it are almost any (muscular, cardiac, hepatic [from liver], hematological [from blood], etc).