My eletic bill shot up to double from 150 to300 this month. Could my heater be broken or my thermostat ?

More than likely it is because it got colder and you used more electric but it is possible if you have a heat pump it could have stopped working and that is the reason for the higher bill.

Also utilitys have increased there prices and will continue to do so in the future.

Have your heat pump checked if you have one and turn down the thermostat if you want to save money.