Is it an almost fishy smell? From what I remember when I had ostomy I was still producing discharge anally, that had a kind of fishy smell. This was considered normal, and is actually a good sign, it means the bowel after the ostomy is still actively replacing skin cells and bacteria.
The stoma I had was a loop ileostomy. This was still connected to my jpouch. For some reason the surgeon was adamant it wasn't connected, but on occasion i passed food from the previous day so I know for a fact it was.
You have had a few ops around the stoma site, maybe you have a leak and a bit of back wash from the pouch. Definitely worth getting it checked, but if the docs says your not connected, take that with a pinch of salt.