Watermom has been giving you absolutely the advice you need. But if you don't test and adjust the FC 3 times a day (or, minimum 2x a day), you'll never get it sorted out. Keep doing what Lisa's telling you.

Meantime, let's look at your pump and filter.
1) You need to be running it 24/7 until it's clear.
2) You need to vacuum the pool to waste every single day. Get the junk out!
3) You need to brush the walls and bottom every single day. This knocks the algae loose so the chlorine can kill it.
4) You need to backwash your filter whenever the pressure rises. So...backwash, and note the pressure. When it goes up 5 psi, backwash again.
5) Get a small box of DE powder, 10 pounds or less. After backwashing, add about 1/3 cup to your skimmer and wait about 20-30 minutes. The object is for the pump pressure to increase a little, about 1 psi, no more than 2. At this point, the DE will improve the filtering for the sand. 10 pounds of DE should be less than $10. And it should last you all summer, if not 2 summers.
6) Get skimmer filters. These are generically called "Skimmer Socks" but can be called "Filter savers". It's an elastic filter that goes in the skimmer, about 4 or 5 for $10. I find one lasts a month. Rinse it out every single day or when it gets clogged. It will catch all kinds of stuff for you.
7) You must have P.O.P.P. Pool Owner Patience and Persistence!

Carl