How old are you? How is your diet? How is your health? Do you drink alcohol? Take medication? What fabrics do you wear?
Any or all of these may affect the underarm odor. The body uses sweat (lymphatic system) to flush out or dump toxins (Then bacteria feed on these substances causing the odour). Whether from illness, diet or bodily processes.
Since it started 8 months ago, you may be able to pinpoint what changed then. And take away those things and see if it helps.
If you wear synthetic fabrics, it may be impossible to do without odor. Try wearing all cotton shirts for a few days and see if that helps.
Drink lots of water to help flush the body. You may have to hit the bathroom more often, but that's preferable.
As a suggestion, the salt rock deodorant seems to have pretty good refernces all around, it is fairly inexpensive and lasts about a year, dries upon application does not have a residue.
Also clorophyll has been mentioned by many to work wonders - and activated charcoal. Both are taken internally.
However, I would do the 8 months ago analysis and see if you find the root: Maybe you started some medication, or changed your diet, or took Antibiotics
that killed your good bacteria, etc. etc.
In any case, the crystal deodorant rock is sold at vitamin shops, wholefoods market and many health food stores and supermarkets.
here is a link with a short commentary after experimenting some underarm dedorizing methods:
Hope you find somehting that works for you,