I have struggled for 3 years now with uncontrollable algae and I can't keep my pH balanced it is always too low. Could it be my filter not filtering properly or my pump is too small for the pool.

I have a summer escapes 16'x42" I am currently using the pump that came with the pool. Frankly, I'm tired of absorbing money into this because I always have to buy algaecide, pH increaser, and shock and it never works.