Oh, don't worry. The problem is that you need to be able to wield the weapon you are using with one-hand or else you'll get staggered. This is because even when you wield it two-handed, the game thinks you are still using it as one-handed but with the STR parameter boosted. So an easy fix is to just level up your strength to the one-handed requirement of the sword you are using if you don't want to get staggered. A quick test to see if it works is if you try a low strength requirement greatsword such as the Bastard Sword and tell me if you still get staggered even if you have the strength requirement for at least the one-handed. That's all I have for now, hope it helps!