LG model lfx25978st 2 door fridge:bottom drawer freezer

PLEASE HELP A POOR $$ MOTHER OF 3: my 4 year old LG lfx25978st (bottom drawer freezer) fridge has stopped working. Compressor, computer, lights, fan at coils all working...I have cleaned dust and any debris aka dust bunnies inside and out. Left it unplugged, doors and drawer open for the last 18 hours with no water results in the drip pan. So doesn't appear to be the defrost mechanism being covered or choked closed. PLEASE HELP, S.O.S