It seems I have been in a similar situation. My ammonia and nitrite sat at .25 while my nitrate was zero. Once my ammonia went slightly about .25 my nitrite went up to .50, now my nitrate has climbed to 20 ppm
. The lesson I learned was that it does take "weeks" not days to cycle and that it will happen as the research indicates. I have not added any chemicals other than to treat my tap water for chlorine (Stress Coat). I am using fish to cycle due to lack of knowledge of the fishless cycle, but all seems well. Going to due a big water change due to nitrite level, but I should be close to cycling (a week or two).