Looking for some people to help with..

Multiplier in general. I am by no means a “try hard” or “pro player”. I am looking for some overall tips and strategies that can help me in pretty much all game modes. I am finding the learning curve from keyboard and mouse to controller to be pretty challenging for some reason. I played a mix of fps on xbox over the years. Although, I am struggling with Halo 4. When I played on release I seemed to do pretty decent. Now I feel my overall performance is just sluggish. My aim has seemed to become way off. I also feel like I pull the trigger as fast as the other player and still get killed using the exact same weapon. I am getting alot more deaths than kills now overall. I feel I have tried everything to improve my game only to find I am doing worse. Any tips on aiming better with a controller or Halo in general would be greatly appreciated. Thanks in advance!

GT: Tridune