Foot tiredness. Any test/treatment.

I feel very tired, sleepy & lack of energy after small tasks like going to market/cinema hall, dusting , mop etc & also excessive tiredness in sole (bottom of feet) especially in summers. Last year, my health reports were ok except very low vitamin d lvl & i took weekly 60k supplement for 2 months & now taking it monthly. I also feel mild pain in left knee while walking in stairs from last 2 months. I hv no friends,so no phone calls, I remain at home mostly, preparing for gov job exam through self study & internet. I feel a kind of sadness, loneliness, tension & lack of enthusiasm/energy. I sleep late (2-3 am) and get up late 9-10 am. I hv problem of shyness/nervousness while talking with people. My tummy started showing out but hands are thin like skeleton also I have less physical strength/capability than other people of my age. I don't eat junk food/smoke/alcohol/tobacco etc. but eat biscuit, mixture etc. Please suggest any test/treatment. Thanks...