2009 Camry Check Engine Light on, It has low power and is shaking

No my question is do you HAVE to use an OEM waterpump from the dealership or can you buy one from Auto Zone and use it? We bought one from AUtozone but it didn't solve the problem and took it to a mechanic and he said we had to get an OEM waterpump from the dealership.

At first it needed the water pump changed, we changed it out it ws fine, then last week the check engine light started coming on and off, had a mechanic check it out said it needed an OEM water pump that we couldn't use any other kind, cylinder 2 & 3 were misfiring, and the mechanic said some other stuff too. Well my Husband changed out the coils yesterday but it still didn't help so then he figured it was the fuel injector, The car has loss of power and it shakes. Just found out the car has warranty and was going to take it up to the dealership and white smoke started coming out of the exhaust pipe and smelled of antifreeze.