Hello, It sounds as though you may have a pilonidal disease which creates an abscess or sinus in this cleft. Treatment is incision and drainage, and antibiotics if it is infected, which sounds like your doctor is doing. If it is more severe, more definitive surgery is needed so that it doesn t recur. I m assuming this is a pilonidal problem but without seeing it I can t say with absolute certainty. However, what you are describing and the location is likely to be a pilonidal abscess. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr Bonnie Berger-Durnbaugh, General & Family Physician