It's very hard to tell what's going on without good numbers. That's why we always suggest you invest in a good test kit, one that uses the FAS-DPD Chlorine test (not to be confused with the DPD test). You CANNOT rely on strips to give you precise information, particularly on CYA levels.

In lieu of that, you'll need to take a water sample to a pool store and get them to test it and provide us with the following information:
Is your pool vinyl or concrete/plaster?
How many gallons?
Do you use an SWG? (if you don't know, the answer is probably not)
FC (free Chlorine level)
CC (Combined Chloramine level)
pH
T/A (total alkalinity)
CYA (Stabilizer/Cyanuric Acid).
CH (Calcium Hardness)

Since you have a MAJOR Algae bloom you are going to need lots and lots of chlorine to kill it.

Now I suggest you look at PoolForum and see that there are various categories and within them are Stickie'd threads. Read those threads because we've discussed this many, many, MANY times and the advice is pretty much the same.