you can build H-bridge using 4 transistors BJT or MOSFET, google H-bridge and you will find its design, also check IC L293, may be available in your market.
I think now you know about H-Bridge configuration
U can use TIP122, TIP127 transistors for four switch for changing the polarity of the DC motor to rotate in two directions.
And use PWM to control the speed of the motor like give a square wave to the motor and write two delay one for ON time and One for OFF time make OFF time delay bigger and ON time smaller it will reduce the speed of your motor.
thanx
If u have any ques pls inform.