mauried:
You arnt turning the hi side fets on properly.
You need at least 10 volts between the gate and source to turn the fets on, and that means that if you only have a 12 V supply
you need at least 22 volts to turn on the hi side fets.
Google H bridge driver to find a suitable driver chip for your circuit.
So what your saying is that i need to apply 22 volts at the gate of the upper mosfets ?