Sounds like it's in limp mode . Is the check engine light on , or a yellow wrench symbol ? could be a problem with electronic throttle control . Have a scan tool hooked up an checked for DTC'S - diagnostic trouble codes . Your gas pedal has sensors inside that wear out , also throttle position sensors inside the throttle body ,this sensors are inputs to the PCM - engine computer .

This sounds like you throttle body motor or position sensor go to autozone and have any codes read from check engine light illumination