I went to get a regular vision test and was told my eye seemed swollen behind. i have to see a specialist and i am scared. what could this mean?

Many options: You are probably lucky that this was found. There are a number of reasons for swelling either in the back of the eye or behind the eye. I am guessing you are seeing an ophthalmologist who can sort this out for you. Eye treatment has advanced significantly in the last decade so I wouldn't worry at this point. Just be curious as to what it is.