well it is a little curious that your reading amonia. did you use the shrimp method? is the shrimp still in there?
Nitrites really should go to 0. Amonia is removed from your tank by being converted to nitrites. Then nitrites are converted to nitrates. THe nitrates are the hardest to remove, when they are removed they are converted to gases which escape through natural gas exchange at the water surface.
If you used a shrimp and the shrimp is still in there, it could be possible that the shrimp is just producing more ammonia that the tank can handle. If nitrites had risen previously but have now fallen to 0 and nitrates are starting to come up I would say your cycle is over. Remove the shrimp do a partial water change (about 5 gallons) and get yourself a fish
You need something in there to produce ammonia to keep the bacteria alive so you might actually want to just leave the shrimp in there keep producing amonia until you have your fish and they have gone through you QT
period. (check out our articles on Quarantines