you are only supposed to have a 1/2 inch of play in your timing belt.. meaning if u were to take the front portion of it & twist it.. it will only turn 90deg. u might want to check the tensioner..

also like bambrose said.. you may be in need of a valve adjustment, it's not a hard job.. just tedious & time consuming.. if your not comfortable doing it.. i'd take it to a shop. Best of luck to ya.