Can low potassium be causes stress & anxiety ? also have low vitamin d

No.: Low potassium does not cause stress or anxiety. Spontaneously occurring low potassium in conjunction with hypertension is often related to hyperaldosteronism. If you do not have high blood pressure I would not worry much. Vitamin D level greater than 20 is normal according to some experts and 30 according to others. Migh want to look at your level more closely.