What could cause me to see things out the corner of my eye and frequent headaches?

Many causes: You could be experiencing floaters which is when the gel of the eye called the vitreous breaks up in the eye and floats around, casting a shadow on the retina so that you perceive a visual disturbance. Headaches are not usually a cause of floaters. If your vision is distorted with headaches, it could be migraine. Please see your eye doctor for an exam and diagnosis. Good luck!