fluctuation of power 50volts verses 180volts

I live in a small town in Montana. For the past week we've been having large voltage spikes. I've been troubleshooting with a digital voltmeter. There are big differences between the two 120 lines in the breaker box. One side will shoot up to 180+ volts and the other will drop down in the 50's and sometimes it will reverse it's self. If I flip the main switch and turn it on again sometimes it will normalize to 120 on both sides. When I turn off the main switch and check the lines coming from the meter I get a stable 120 volts on each line. When I turn on the main switch with the voltmeter still connected the voltage from the lines to the meter drop and raise to what ever the house is pulling. I've gone through each of the breakers and noted the voltage fluctuations. I can raise or lower the voltage of a line by turning the breakers on and off. At one point I had all of the breakers turned off except for the outlet for the fridge. When I checked the outlet it was 120 volts. I kept the voltmeter plugged into the meter and then plugged in the fridge. The voltage dropped from 120 to 43 and popped back up to 120 when I unplugged it in again. The breaker box is grounded with a rod driven into the ground and connected by a copper wire. Sure could use some help. Thanks