my sister inlaw had the same problem it was making her life hell, she went to her doctors and a few months ago went and had an op to remove her sweat glands under her arms shes great now oh and smells better ha ha
My daughter has just come out of hospital after having an opertion to sort out her sweaty palms. The results are instant and she is recovering nicely. See your GP, I also remember a friend having an opertion for sweating armpits back in the 90's.
I hope you get it sorted as I know this must be embarassing for you. Good luck.