Unfortunately I do not have any information about your food intake and medical history. But, I have seen this symptom very often, go to your doctor, request him to control your blood chemistry, it may be because of iron deficiency.

With food rich in iron like red meat, eggs, nuts and seeds, legumes and pulses, beet roots and other vegetables you can increase your iron status without any problems. It takes time to improve the iron content to normal values, thus increasing the red blood cells which transport oxygen to all cells in our body, less oxygen means, weakness and tiredness.

About iron supplementation, I am against this because this makes more problems to our body than an iron deficiency. Two to four weeks is the maximum time for iron supplementation. Foods or vitamin tablets fortified with iron must not be taken excessively because iron in high concentration is poisonous to our body.