Hey guys, I put the circuit on a breadboard, but the output wave looks like a capacitor charging and discharging, where could I have gone wrong? Do you need the picture of breadboard as well?
Also the gain is only 6 (supposed to around 18 according to my calculations)

 

The contacts on a solderless breadboard are intermittent and cannot pass the high current of this power amplifier.
Why don't you solder the parts on a compact stripboard layout or on a pcb?