If it's always the same sting(s) you break there wil probably be a 'sharp spot' at the bridge. You'll have to smooth it out then. Don't know exactly how, but maybe using a vile ? I'm sure other ppl can answer that question.
I used to break lotsa strings before too. But I've found a way to let your strings last longer. After you've played you should take a tishoe and twist it so you have something shaped like a pen. Put it underneath your strings and slide it up to your nut and then take it back down to your bridge. You see all the dirt that came off ? If you do this every time you played long sessions your string will last hulluva long !
Also, washing your hands before you play will help your strings last longer. I can't stand playing with sticky hands ! I really feel icky when I have to play on another guitar that is sticky.

Hope this helped