The first thing wrong is that the 3 inch tablets are extremely acidic, so you're driving the pH down with the tabs and trying to raise it with Borax, getting a net result of zero. Stop using the tabs and switch to bleach, and it will help.

Second, are you using test strips or drop-based testing? Can you use the dilution method to better estimate your chlorine? High chlorine levels (above 10 or so) can give false pH readings..usually will show falsely high, but if you're using test strips, high chlorine can bleach out the strips altogether to give you a falsely low reading. You also don't mention your CYA level, which would help tell us whether your chlorine is actually "high" or not, since the chlorine level has to be proportional to the CYA level.

Third, in addition to adding Borax, you can also help raise pH through aeration....kids splashing, return eyes pointed up to the surface, water fountains, anything that will cause bubbling at the surface of the water.

If you have a vinyl pool, it is imperative that you raise the pH to at least 7.0 ASAP--if it's below 7.0 it can damage your liner.

Janet