First off: What are you testing with?
How big is your pool? Cannot estimate how much chlorine you need without that.
What is the ingredient of your "shock"? We HATE using "shock" as a noun rather than a verb here, because as a noun it can be ANYTHING--Cal-hypo, di-chlor, tri-chlor, lithium, "non-chlorine shock", sodium hypochloride. These things all add chlorine (except the non-chlorine) but add other stuff as well.

Plus, if you have algae, you have to kill it before the chlorine level can be maintained.