You need a dermatologist.

There are shampoos that are advertised for "smelly scalp" (in addition to oily scalp). There are some interesting ones from South Korea that you can easily buy online in the US. I think they cost anywhere from $15 to $25 per big bottle. These are high quality products with lots of Asian herbs that have been used for centuries and longer. I don't know if they actually work for smelly scalp but some internet sellers might offer free returns.

I have personally used T/Sal shampoo (different than T/Gel and it cleared up my years of scalp acne almost immediately and it has not returned after I stopped using just 1 bottle.