Maxy, how old is your tank, if the Ammonia is still up the Nitrite and Nitrate probably are as well, you may need to do more than weekly water changes to keep the Ammonia and Nitrite levels down until it cycles properly, how often are you cleaning out the filter?
It does sound like a very heavily stocked tank, just under 50 fish by the sounds of it. You may find it is hard getting the tank to cycle properly with a heavy load straight away, usually you start out with a few fish (say 1/2 a dozen or so) and stock up slowly allowing enough time for the bacteria to adjust to the waste load. Doing extra water changes will help, 10% daily would be a good way to keep the Ammonia & Nitrite levels down.