This sounds like a typical failed drainfield.  The hole you dug probably gave the water a path of lessor resistance to flow into instead of back to the septic tank.  You need to solve the issue of the drainfield absorbing water before the problem is fixed.  Septic-Scrub treatment can help do this.  

You need to find your distribution box, remove standing water from the field to at least a few inches below the laterals, and add Septic-Scrub.  

If you wish to discuss your particular situation before you treat the system, please do not hesitate to call.