Car problems GMC Envoy 2002?

My car has been doing funny things. I'm terrible with cars so I'll try my best to explain. Sometimes, not all the time, when I press on the accelerator the car will just slow down and then lurch into speed (especially on hills). Also sometimes when I am sitting at a stop light the car will start shaking pretty bad. I'm scared! Did I mess up my car really bad? Is this going to turn me into a pedestrian??