I Have Swelling Between Anus And Scrotum From Last 8

I have swelling between anus and scrotum from last 8 months. Starting stage i see the doctor they priscribed antibiotics I have it then 3 or 4 days after reduce swelling and pain.after the 4 days it again swelling and pain. Again I have antibiotics it again calm down. Now also it is some days calm down some again swelling and pain plz suggest me what it is and how treat it