Transmission problem, car won't Move in any forward gears, only reverse.

The car had been sitting for about a year and then I drove it for a half a day, the transmission seemed to be slipping. I checked the transmission fluid and the level didn't register on the dip stick. I went to drive it the following day and only moved in reverse. I put 5 quarts of transmission fluid in it, which brought it up to reading normal on the dip stick and still the same problem, only moves in reverse.