Furnace is 1 year old and thermostat probably 8-9 years. Woke to 10 degree temperature drop. Checked breaker and furnace switches. They were good. Changed batteries. Digital display did not show.I wiggled new batteries and began to heat so went back to bed now. 81 degrees and I shut off. Reset seems to be a hole. What can I do. I am low income so hope I do not have to replace. It is model 429999B