Jerking wheel while turning

When turning or going around corners my wheel will want to turn early to correct itself. It wants to go back to twelve o'clock while in the middle of a turn and will keep jerking until it gets back. I added power steering fluid because it was low and it did not fix it. I tried opening the power steering cap and turning the wheel to get any air out, it felt like it worked at first but was still semi jerking and went back to fully jerking. Any information would be great.