I used to have this problem and it made my life hell. I couldn't go anywhere without worring about the embarrasing sweat stains. Finally my mom took me to the doctor and he prescribed drysol. It is a roll on liquid that you rub on right before bed under your arms and you wash it off in the morning. The first time you use it it takes a few applications to work good, but after that one time and you can be good for a month easy. You can get it off ebay for about 20 bucks a bootle, and if used right, you can get a year or two from a bootle.