I get a pain in my eye everytime I move it. When the pain happens a big black dot appears in my vision. What could cause something like this?

Inflammaton. Read pain with eye movement can be a sign of a serious eye problem like inflammation of the optic nerve; however, a small back spot or spots are floaters and usually are not anything significant. If it is a large black spot obstruction your vision then it may be bleeding or some other inflamed problem with the retina, then I suggest you be examined by an eye md, that is an ophthalmologist.
Eye Doctor. I don't know how old you are, but it's a good idea to have your eye pressures checked and your retinas looked at by an eye professional. It might be an easily treated problem, but it needs looking at.