I Am A 57 Year Old Male. I Am Feeling

I am a 57 year old male. I am feeling pain in the hip flexor area and it seems swollen. The pain will go down my right leg and around the hip to the back area particularly when I walk. I am also experiencing fatigue and lack of energy. My doctor prescribed bacterial antibiotics because he felt something in the lymph nodes. However, they did nothing. I am going in for an ultra sound tomorrow to see if anything is in there. I exercise regularly and have lifted weights all my adult life. Do you have any thoughts on the cause? Thanks, Joe