Breaker in breaker box to one bedroom tripped, changed out switch to overhead fan but breaker will not reset.

How does the breaker react?

When you reset the breaker, move it as far to the Off position as you can, then move it to the On position. If the breaker immediately back to the Off position, you have a short in the circuit.

What else is on the circuit besides the switch and the fan?

Why did you replace the switch?

What wires are connected to the switch?

Is the switch wired from a connection in the ceiling or is power coming from the switch outlet to the switch to the fan?