It depends on how much water your pump is pushing, but generally it should be running 10-12 hours a day (less during the winter when the demand is smaller). You might have low salt levels. Are you testing with strips or do you use the cell readout? If you're reading the cell, go get a strip test (it's more accurate).

easso,
Chlorine levels with a chlorine generator are a function of how long you run the equipment and at what percentage you set the generator. A pool your size should turn over the water in about 8 hours depending on the pump/filter/plumbing flow rates.
Most of the salt gens. are rated at X number of lbs. of chlorine per day. I'm sure the manufacturer calcs. are based on the filter running 24 hours a day and the salt gen. running at 100%.
Your specific run time will be affected by water temp and bather load. You'll have to experiment a little. Start by running your pool 8 hours with the salt gen. at 100% and then adjust it from that point. Generators will shut down when the water temps are low. When water temps reach 85+ you may need to supplement the salt gen. Good luck.

What is your CYA reading? If to low you will burn your chorine off almost as fast has you produce it

What is a cya reading Also thank for all the replys

CYA is cyanuric acid aka Stabilizer. If you have zero in your pool, the chlorine will dissipate almost as fast as it gets gets produced. I had this problem on my new pool start up. After I added a $40 bucket of CYA, I was making tons of chlorine and it wasn't dissipating. More from Wikipedia:

Cyanuric acid is used as a stabilizer in recreational water treatment to minimize the decomposition of hypochlorous acid by sunlight in outdoor swimming pools and hot tubs. It achieves this by absorbing UV radiation.

Chlorinated derivatives of cyanuric acid, such as trichloro-s-triazinetrione and sodium dichloro-s-triazinetrione, are used as algacides or microbiocides in swimming pool water and large scale water systems in industry.

Testing for cyanuric acid concentration is commonly done with a turbidometric test, which uses a reagent, melamine, to precipitate the cyanuric acid. The relative turbidity of the reacted sample quantifies the CYA concentration. Referenced in 1957.[5] This test works because melamine combines with the cyanuric acid in the water to form a fine, insoluble, white precipitate that causes the water to cloud in proportion to the amount of cyanuric acid in it.