There is actually a medical term for terrible underarm odor; it is called bromhidrosis. Special kinds of sweat glands called apocrine glands are located in the skin of the underarms, breasts, and genitals and are responsible for the condition.
Bacterial breakdown of the secretions of these glands leads to the production of a number of substances — including ammonia — that cause the foul odor. These glands are more active in males, so bromhidrosis is more common in men, but many women suffer with it as well. Medical conditions such as diabetes, obesity, and skin problems can also lead to the presence of these odor-causing compounds.
A number of approaches can work toward relieving the problem. The least invasive include intensive local care with antibacterial scrubs and topical antibiotics, antiperspirants that contain aluminum chloride; electrolysis to remove hair and limit bacterial growth, and the treatment of any underlying skin conditions.
Diet may also play a role, so you might try eliminating alcohol, garlic, and onions to see whether the condition improves.
Another possibility is 20 percent aluminum chloride, which is available from a pharmacist (ask for Drichlor, Anhydrol Forte, or Perspirex); this is pretty strong stuff, so be sure to use it only as directed and be careful about ruining your clothing.
Also keep in mind that changing your clothes often can help, as the odor may become dried into the fabric.
Bathing is of course very important.
I would recommend getting a referral to a dermatologist before you try any of these home remedies. Since you already know you have a yeast problem.......the doctor will be able to factor that into his diagnosis and treatment plans to help you.
I'm sure there is a treatment/cure for your condition and I wish you the very best.
Have you tried purging and cleansing your body. Look into trying a herbal cleanse and monitoring your diet of greasy and sugary foods for now. Then using golden seal as a tonic.
Rub half a line on each armpit after taking a shower. It worked for me and my aunt. We both had that problem.