H-Bridge not pulling enough power
It's pretty clear that what you're trying to do is something like







simulate this circuit &ndash; Schematic created using CircuitLab

where you apply 9 volts to one NPN or the other, depending on the direction you want. For the resistor values shown you'll get base currents of about 14 mA, which should give you a decently-saturated output for 3 amps of motor current. If you really expect 4.5 amps, I suggest you halve the resistor values. Motor voltage should be around 20 to 21 volts, assuming your 9 volt battery is up the task of providing a real 9 volts at the current levels indicated.

Please note that you need to do some research on "flyback diodes". Your schematic doesn't have them, and you are at some risk of destroying your transistors.