Get a test light and see if your getting power to both metal tabs that hold fuse in place (with key on). These tabs corrode and need to be cleaned, best to do em all. Best to disconnect battery cable when cleaning these (all fuses removed). This can keep it from working even with a good fuse.
If the fan motor occasionally squeeled or made bad noises before when it was running you could be looking at fan motor replacement. Guarenteed, this is one of the most frustrating things to replace on your car. Bad resistor is another possibility although usually one or two speeds will work when these are failing. Resistor is as difficult to replace as the fan motor due to its location inside of the heater box.
Someone on BB has photos of heater fan motor replacement. Pretty well have to totally disassemble dash.
Good luck-