Robin,
Yes, get it tested and plan on getting your own good test kit.

Guessing at problems and then throwing in chemicals is the second fastest way to get into pool trouble. The first, of course, is pure neglect.

Also, I believe in the Occam's Razor method (the simplest solution is the solution), very similar to the K.I.S.S. method. Start at the beginning: Chlorine, pH, Total Alk, CYA and Calcium levels. Don't go on to metals until those are fixed (well, calcium IS actually a metal, but we never see it as one, just as a salt. Throw calcium metal in water and it boils, which is better than sodium metal, which blows up!)