yeah, doctors aren't really sure what causes it exactly. there are different plausible causes and different types.
that's also why i asked how old you were. usually it starts in your mid to late teens. some say it's genetic. they say that what happens is that your nervous system just happens to be too sensitive to stressors for some reason. this triggers what they call a "fight or flight" response from your nervous system and the sweat is some sort of defense mechanism.
some doctors have also said it could be accentuated or caused by high blood pressure, diabetes, obesity, thyroid gland problem, etc. if i was you i'd get checked out first to get a proper diagnosis, second to rule out the thyroid gland reason if you really have hyperhidrosis. there are some treatments but no real cure. treatments go from medication to special creams/lotions to botox to even surgery. it really depends on what type of hyperhidrosis you're dealing with.
things that could help:
try to reduce blood pressure
try to reduce body-fat
meditation, breathing techniques, relaxation
try to reduce spicy food and avoid caffeine
lower sugar
drink sage tea
and go see a doctor about it. it's usually not life threatening (unless it's a symptom of something else) so it's not like you're gonna die or anything. it's just a pain in the ass sometimes.