I did two series of the Botox injections about ten years ago or so, and somehow, I "broke the cycle" or something, and while I sweat a normal amount now, I don't pit out a t-shirt in ten minutes anymore. I wouldn't hesitate to do it again, or the other, surgical option.
Sweat *is* sexy, and it's fine when I'm at the gym, or in really hot weather, or whatever, but big wet circles in February is just weird. Now I don't even wear pit stick.
I agree, though, see a dermatologist. Excessive sweating in a normal-weight person can be a sign of a medical problem if it's of new onset.