When I cycled my tank, It took about 40 days. Around 30 days everything started going, ammonia dropping, nitrites and nitrates started going off the charts. Soon (about 2 weeks) ammonia and nitrites started going down, until I had to start adding ammonia once in the morning and once at night.
Just keep testing the water and eventially you will start seeing a change. It will not happen fast.
Make sure you turn your heater up to the highest temp, and keep running your filter, and have lots and lots of patients.
Also I have read that you need to keep your lights off. Bacteria will grow faster that way. That is what I did.
Oh and almost forgot.. I bought a marimo ball from Petsmart and I stuck that in my tank without rinsing it first, I believe it had enought bacteria from their tank to help seed my tank even if a little.