Noisey Fan Belt

hi-

i drive a dodge spirit. every time i start the car the fan belt squeals! if i press on the gas the sound gets louder! i have to wait for it to stop squealing before i put it in gear and go.

also, when i run the heater it squeals until i turn the heater off.

do i need a new belt? can i use a spray like Belt Dressing to make it stop?

thanks!