If you have been having panic attacks for 4 years, you do need to see a doctor and see if there is anything else going on. Having panic attacks for so long and not seeking treatment can have severe affects on your body that are irreversible and serious. If you still don't want to see a doctor knowing that, then here a some things that might help you out.

1) Reduce the amount of caffeine in your diet.
2) Breathing exercises.
3) Exercise.