Car revving but barely moving.

I have a '97 cavalier and when i press on the gas, the car revs up and barely starts moving. when it gets to a decent speed, it trys to shift but goes back and forth between high and low gear. There is also no way i can get up hills from a dead start. it just revs. My car also wont go in reverse. The check engine light was on and it turned off when i poured a quart of transmission fluid in, but it was still doing the same thing. I can't check my transmission fluid either because there isn't a dipstick.