Septic tank help !!!

I have been having problems for a few months now . My tank has been pumped and was filled again in short order maybe a couple of weeks. We had the fill limes replaced 5 years ago and until November of 2013 everything was fine. The water is backing up into Tue toilets and sinks regardless of how much we conserve water. We don't let any go down our drains. We have the shower clogged and shopvac the water out and dump it. Washer drains to the shopvac and is dumped, dishwater same thing and were lucky if we get one toilet flush a day only if its not raining of course. So I dug the lid to the single compartment 1000 gallon tank and its full. So I'm thinking the problem def is from the septic to the drain field. A guy came out and said we can add another 100 ft of fill lines for $15 a foot. I don't think that's gonna fix it. Can someone please help me . I do not see any clean outs vents or nothing for the lines or tank . I need help bad please help. Thanks from Georgia Tweet