It may be the idle air control valve. Sometimes they get gunky and can get stuck in the open position, which can cause you car to act like you're pressing on the gas a little even when you aren't. They're usually fairly simple to replace, just two screws hold it in on the throttle body. You should be able to get one from a junkyard for a few bucks or even free if its bad, or you can even try taking yours out, spraying it with engine degreaser so it gets unstuck (read instructions on can of degreaser) and putting it back in. I'm a tiny female who can barely work a screwdriver and I fixed mine myself when the mechanic quoted me $200 to replace it.
Also look for a vacuum leak, or a sticky throttle plate (carbon build up), or a broken return spring.