I'm sorry to hear you're having problems with your tank Jacqueline. The people on these forums will be happy to give you a hand.
One thing I noticed in your conversation with roydooms that I wanted to ask about.
I highlighted what I thought you might have been answering, you haven't done a partial water change (PWC) in the three weeks your tank has been running? If that's the case, and it hasn't been cycled, I suspect that your ammonia (and possibly nitrIte) levels are off the charts. I hope you can get the API freshwater test kit and test ASAP, because high levels of ammonia and nitrIte can kill your fish.