Low ph reading

[gardennorm]

Hi Ive just got my TF-100 test kit and have used it on a pool im having trouble with.
All the readings are ok except for two

CC=0
CYA=200 approximatly

Ive used the pool calclulator to work out how much water to change to bring the cya level down to reasonable limits

I currently have a very low ph reading and always have had regardless of how much PH+ ive added
currently ive added about 15kg over 2 months to a 31600 gallon pool.
Will the PH reading be affected by the very high cya level
also I always top up the pool with fresh water to maintain the correct level will this have any affect on cya or is the only option to partially drain the pool

many thanks