"On the information given, the most likely cause is a simple floater. This is a change in the vitreous humor of the eye which casts a shadow onto the retina. If this happens to be in the line of sight, it will move with the eye and always appear directly ahead.
Floaters rarely indicate serious problems, and most people acquire a few over time, but a sudden fresh batch of floaters, especially if accompanied with any bright flashing lights in the vision, should be followed up medically for the UNLIKELY (2% max) chance of an early retinal detachment.
There's really nothing you can do about it besides put up with it. They're caused mostly from major stress, lack of sleep, extended drug use or severe head trauma far as I know.
After reading some of the comments of people experiencing the same thing as I do, I feel less worried now but I'm also concerned that is my right eye starting to age??? Because most people said that these "floaters" are a natural part of the eye's ageing process. Probably my age now is 20 and my right eye is going to be 50 soon! hmm..