Any way to change key assignment for fire mode (single, burst, auto) in BF3?

I've only just purchased BF3 I play the assault class a lot and I try to revive as much people as possible. The only think i f*cking hate is the assignment of the D-pad for my xbox controller. 9 out of 10 times after having used Dpad-right (defib paddles) it also pressed dpad-down in the chaos, changing my weapon from auto fire to single fire. A lot of times, I get shot because the fire mode changed and I don't notice it.. After reviving I want to shoot some people to find out the fire mode changed and I get killed because I shoot one bullet instead of spraying like a mad man. Any suggestions on how to overcome this? ps: don't tell me to not press down, because it happens automatically.. my dpad is sensitive ☹️