Goldfish Trouble

I have two small goldfish, the kind they sell at Wal-mart for I think 40 cents? After having them for about a month, we noticed a very tiny baby goldfish in the tank with them so we assumed they had eggs and we really didn't notice because anytime the tank would get dirty we would clean it right away. Now we still have the two older goldfish and the baby goldfish in the same tank and one of the older fish is acting really strange, staying at the bottom of the tank, having a hard time staying afloat, etc. We thought maybe it was going to die but now it's been about a week since it's been acting like this. We also noticed that it's staying next to a big pile of debris that has gathered in the tank and the tank does have a little cloudyness to it. Please help I don't know what to do, if it is laying eggs I don't want to clean the tank out and wash them away! Thank you.