I have water seeping up through the slab in the laundry room. I checked the water meter early one morning and then 2.5 hours later I checked it again and about .3 gallons had leaked during this time. I was home alone and am absolutely positive no water was used so there's a leak somewhere. My question is how do I go about locating the leak without tearing up the whole slab? I would appreciate any advice on this because I can't afford to pay a plumber to come out and fix it so I'm going to have to do it myself.

If you have an outside leak, odds are you won't have a lot of choice... because that's a HUGE job escavating between the house and the meter to find the point of the leak before you can even fix it. If you are 20 ad strong it could take you days to dig it up by hand, if you are old then forget it... unless you have access to a backhoe and know how to use it. It's a job beyond the average person.

Trust me... I do almost everything... expect I paid to have a new driveway put in because it was way beyond my skillset... and I pray I never have to do that one because its way beyond my abilities due to the amount of work.

There are companies that specialize on finding leaks. American Leak Detection is one, my son works for them.

This is NOT a job for the homeowner. You must first locate the leak and that's not easy to do. Water like electricity will seek the path of least resistance. So let the leak may be some distance from the wet spot.
To locate the leak under the slab. We call in a company called Slueth that has sensitive listening devices. Once located the plumber can then come in and break open the slab and repair the leak. Your only other option would be to cut that line out and we pipe overhead. Sorry to be the bearer of bad news. Let me know what you decide. Good luck, Tom