Im afraid we have leaks! Maybe slab leaks...?

Off and on for a couple of months now we notices a wet wood smell not musty just more chemical.. we figured it was off gassing of new materials since this is a new place. Now we realize its likely a leak. it begins in the laundry room and travels along the wall where the waste line would go out to the septic tank. The odor comes and goes and IS NOT SEWER GAS... but it tends to show up when we are using more water in the home. We realize now this may have been going on for a long time. There are NO wet places on carpets or floors . We fear there is a small leak in a wastewater line and its seeping between the walls along the studs. Here is one reasonw e feel its wastewater lines... Today we washed numerous loads of clothes with Bleach.. the bedroom the line runs paste got a very bleachy smell and the kind of smell youd get if you put bleach like on wood or soemthing... that convinced us its wasteline.. WHich concerns us because we do not know if that also means toilets could have been leaking into the wall as well!!!! OMG! We plan to open the wall in the laundry room on Monday hoping to see if we can see something obvious nad find out if there is mold growing in the wall. Id like input from people hwo may have advice about this situation, ideas suggestions etc...

We are hoping its something obvious that maybe loosened from a washer vibrating the floor and will not be IN the slab! if its soething like that we can fix it.. long as there is no obvious nastyness in the wall! else we are in real trouble I thinkl. Im looking for contractors and plumbers to reply to this. This is new construction with PVC drain lines... ranch style on a slab and a septic tank.. but the septic tank is ok and the observation areas in the drain fiedl are dry. ALso rain does not effect this.. only our water use. Please reply with anything you can think of.. WHen the smell comes across in the one bedroom it makes some of us ill.. burns our eyes and nose its like something reacting with something else.. we assume bleach from our washer coming in contact with building materials in the wall but we do not know for sure. IT IS not sewer gas though. We have also noticed some areas of mold popping up in the bathroom and now assume we must have it in our air suspecting it may be in teh walls now.. but again no wet places and no mold on walls coming through.. YET...... We have lived here since last May so this may have been going on a LOOOONG time and we use A lot of water ALOT! we also have birds in the home that are not feeling well.. unsure what it is but seems re\lated to the odd smell.. they improve when its not there and feel worse if it is... good indication this is NOT good!

THANKS in advance!