We will be able to help you much better if you post your numbers:

Free Chlorine
Combined Chlorine
Ph
Alkalinity
Calcium
Cya

The reason is we need to know how high your chlorine should be according to how much cya you have in the pool. This way we can tell if it is sun eating up the chlorine or algae. One good way is to see if you use any chlorine overnight. If you do, then the chlorine is fighting something. Don't feel overwhelmed - we can help, and we can help you learn all about your own pool , and how to keep it clean and clear