One possible cause of intermittent pressure or pulling behind 1 eye is problems with the sinuses. Allergies can also cause pressure behind the eye.

Because of gravitational waves.

You actually can, but most of the time you can bring it back to the center of your eye by gently pulling it. If you lose it in the side, nothing will happen.

Use a cotton pad, wet with warm water, to wipe the eyes. Use a separate cotton pad on each eye.

No. Avoid rubbing the eye, and try pulling the top eye-lid over the bottom lid and rotate your eyes. If that doesn't clear it, or wipe it to the side of the eye, try washing the eye using an eye-bath and luke warm water.