So no fish, nitrates were at .5 now 0. How are you cycling your tank. The cycle can take 2 months or more. There is no set # of days, weeks, or months that a tank would cycle. Do you have a heater on, I heard that speeds up cycling A LITTLE. Are you using ammonia or put media or gravel from another healthy tank. We need to know more info about the way you are cycling. You are not finished yet with your cycle something happened to it recently, do not put fish in there yet.
Not an expert in this part, but read something that the good bacteria can die for some reason during the cycle and you have to start cycle over again or it takes alot longer, don't quote me on that. Hope someone can help soon to explain this to you better.
But when you post, give full details of everything about your tank, so there are not 20 posts from people trying to help you, asking questions to get all the info they need to give you the best advise.
You didn't answer the question, how do you test your water, yourself or at the petstore and what type of kit you have strips or liquid.
The sooner we get all answers then we can advise what you need to do to fix your problem.