I had the same problem for awhile when I had a hernia. I had developed edema(fluid build up) between the bowel and uterus in the abdominal cavity and the lymph nodes in that region were trying to detox me and made the smell there. I solved it by soaking my bottom in an epsome salts bath twice a day and helping my lymph system detox by drinking alot of water and Seasalt , taking chlorophyllin 3 times a day with meals (be aware, this will give you many bowel movements a day) and rebounding (jumping on a mini-trampoline). The smell cleared up even before the hernia surgery.
Hope this helps.