hi there, the lump that you feel could be a lymph
node or could be asccessory mammary gland
tissue. You should visit your physician and get a fine needle aspiration cytology done of the lump. This test is very simple and it will be able to tell your physician the exact nature of the lump and whether you need to worry about it or not. Your tiredness
could be due to lack of proper sleep or worrying about this lump. It is best to know its etiology and put your mind at rest then to speculate and worry about it Take care.