I have a side by side whirlpool fridge and the freezer is fine but the fridge is now freezing everything. It's about 11 years old.

Since you stand to loose all the food I would call a service tech ASAP. But here are the most common reasons for the problem you have.
Cause 1
The Evaporator Coils are Frosted Over The defrost heater assembly turns on a few times throughout the day to melt away any frost that may have accumulated on the evaporator coils. If the defrost heater assembly is defective, frost will continue to accumulate on the evaporator coils, and the coils will become plugged with frost. If the evaporator coils are frosted over, the airflow through the coils will be restricted, causing the refrigerator not to cool. Check the evaporator coils to determine if they are frosted over. If the evaporator coils are frosted over, test each component of the defrost system.
Cause 2
Evaporator Fan Motor The evaporator fan motor draws cold air over the evaporator coils and circulates it throughout the freezer. If the evaporator fan is not working, the freezer or refrigerator will not cool adequately. To determine if the evaporator fan motor is defective, try turning the fan blade by hand. If the fan blade does not turn freely, replace the fan motor. Additionally, if the motor is unusually noisy, replace it. Finally, if the motor does not run at all, use a multimeter to test the motor windings for continuity. If the windings do not have continuity, replace the evaporator fan motor..
Cause 3
Damper Control Assembly The air damper control opens and closes to let the proper amount of cold air into the refrigerator compartment. If the damper does not open properly, it won't let enough cold air into the refrigerator. Check the damper control to determine if it is broken or stuck closed.