Here are a few things to think about for your pH problem

Did you test your fill water for pH and ALK when you refilled your pool?
What test methods do you use?
Any fountains in the pool?
Does your water return break the surface?
When are you testing?
Where in the pool are you testing?

I found by testing next to the return my pH was higher. I am in the process of dropping my ALK slowly and checking for pH raise. Higher ALK in my pool caused my pH to run up every week.
Steve