Our problem started couple months ago but my wife said over a year ago. We are in a two story house. When you flush the toilet down stairs, you hear a gurgle sound/noise in the kitchen sink and sometimes when you use the kitchen sink, this same toilet gurgles. Now the past day, the toilet backed up and when you flush, the water will not go down. It's gotten worst, when you use the sink in the toilet and kitchen, the toilet backs up and the water slowly goes down in the kitchen sink.

Please help