Well, I don't know the reason behind it, but I know I sweat a lot too. I recently bought Certain Dri, which is an anti-perspirant with prescription strength to help you lessen the sweating. It's about $6, and you have to put it on at night, but you're not supposed to use it in the morning, or right after you shave.
Another thing I recently bought was Adidas Absorbent Deo (24 hour "wetness control"). It's one of those clear liquid solid types. I've only been using it for a couple days, but I feel like it's working a lot better than my others have.
I don't know if this helps you lol, but I figured I'd let you know what's out there in case you didn't know yet. Make sure after you sweat a lot that you replenish your body with water and salt. I'm sure you know that when you sweat, your body salt kinda just lies on top of your skin...ick I hate that feeling. But anyway, hopefully someone with more knowledge can tell you what it's actually from.