As per the history you are giving it appears that you have some kind of opaque shadow interfering your vision and causing distress.
Such moving shadows are called floaters
You must undergo complete retinal and optic nerve
evaluation in form of indirect ophthalmoscope that will examine your vitreous cavity and retina.
It appears that there is some vitreous problem like peripheral vitreous detachment
, but other conditions like glaucomaetcshouldberuledout.