The motor does not reverse its direction when you go into regeneration but what does reverse is the direction of current flow. Thus you need a second bridge in regeneration to conduct current in the opposite direction to that when you are motoring. You could also consider using an H-bridge topology. Remember also that when you are regenerating the motor(generator) voltage is higher than that of the battery (which is what forces the current back into the battery) so your voltage regulator will need to sense whether it needs to provide motoring energy (Battery volts higher than motor and forward bridge conducting) or absorb regenerated energy (Motor volts higher than battery and reverse bridge conducting).