Welcome to the forum!
I would guesstimate 10000 gallons is close for now.
You need to follow the
SLAM Process. To do that, you need a proper test kit, see
Test Kits Compared. I suggest the
TF-100 A proper test kit is needed to get the accurate water chemistry results needed to follow the TFP protocols.
While you are waiting on your test kit, add 5 ppm FC worth of liquid chlorine / plain bleach to your pool each evening with the pump running. This will replenish the FC lost each day to the sun and also inhibit any algae in the water from growing further.
I suggest you read
ABC's of Pool Water Chemistry.