Can you post a schematic of how your opamp is configured? There is something seriously wrong, because you show an inverting opamp stage, but your scope trace shows that the output is in phase with the input (non-inverting).
Oh, I went an looked at the schematic on your first post. The 1K input resistor is way too low. Since it is connected between the sensor and a virtual ground at the inverting input of the opamp, it is loading the sensor.
Reconfigure it so that the sensor output goes to the non-inverting input of the opamp as I showed in my previous post. That was based on not having a coupling capacitor, so if you now want one, we will have to provide a dc path for the opamp's input bias current.
You could also change the input resistor to ~50K, and the feedback resistor to ~500K in the inverting configuration you showed.
At what level do you want the output of the opamp to sit in the Hall's nominal resting state?
Here is my favorite non-inverting, ac-coupled gain amplifier. If you use a modern single-supply rail-to-rail opamp, you can power it with only the 6V sensor supply; no +-15V supplies required.