Water is one of those distructive forces of nature that will move mountains and needs to be treated with the respect that such a force deserves. think how with just a few mm's of water pressure, it can find its way though every crack in a flat roof and fuck everything below, think how small leaks in swever pipes can wash away so much soil from around the pipe that as bus can fall into the hole when the road above eventually caves in.

unlike a pipe or a roof with a pool you have 10's of tonnes water trying to push the pool into the earths core and the soil pushing back, there will be settling and the forces across the floor will be uneven. is the floor strong enough to take this without cracking, and are those dry joints you have between the pours been treated to make sure they don't leak? because these cracks have far more than a few mm of water pressure pushing the water though those cracks.

I think most pools become issues because most are built by contruction workers with no understanding of the issues regarding pools and they use the same techniques they would if they were building a supporting wall in a condominium. Its a skill in its self and you need a specialist to design and carry put the work, for the remedial action you need to undertake, this is especially true.

Your challenge is going to be to find a competent expert to advise you and give you advice which is your best interests rather than the experts new car fund. Rather like seeing a thai or american doctor.

Best of luck