CYA stands for cyanuric (or isocyanuric) acid. If you don't have a test kit that can measure these things, can you take a water sample to a reputable pool store and ask them to test for you. They should give you a printout that you can bring back and then post values here. Just don't let them talk you into buying a bunch of stuff. Pool stores are notorious for selling people things they don't need because, of course, they are in the business to make money.

We won't be able to suggest if or how much stablizer (cya) to add unless we know the current reading. Sorry to be so vague, but without these numbers we can't know what to suggest.