96 Ford Probe w/ possible engine problem?

When I accelerate, and it usually happens when I hit 45MPH, the RPM's will skyrocket, and the gas pedal gets hard to push down, and the car wants to slow down. This DOES NOT happen when I accelerate VERY slowly. I am not abusing my car, I drive it like an old lady, and it just started yesterday. What is wrong? I know I can go to Auto Zone and get this checked based on the Check Engine light reading, but the guys at my local Auto Zone are dumb. They don't tell me anything worth listening to. My fiance is pretty great with fixing cars and even he is stumped! I'm trying to avoid going to a mechanic!