Lethargicness is an important clinical manifestation of several important diseases as dyselectrolytemia, diabetes, thyroid disorder, cardiac valvular diseases, hyperlipidemia, major depressive disorder, over stress condition or simply vitamin D or iron deficiency. Since you take good diet,so chance of vitamin D or iron deficiency becomes thin. Investigations to be done are blood for fasting blood sugar, PPBS (2hrs), fasting lipid profile, TSH,T3,T4,RENAL FUNCTION TEST. Untill all reports are done, start your diet daily in morning with one cup of NON-COMMERCIAL GREEN TEA WITH 1tsf honey. You may take it in evening also. Drink plenty of water. Review with reports,when all are done. Avoid taking any sleeping pills at bed time.