Weekly water changes are better, most people do between 30 - 50%! Leaving so much time between WC and doing such a large amount could be harder on the fish since the water's chemistry could differ very much from your tap water. I had it happen that a number of my fish suffered a pH shock and died after a large WC.
As Gizaroo already said, depending on your filter and what you threw out you may have thrown out your beneficial bacteria that convert your fish's waste from their toxic forms (Ammonia and Nitrite) into the less toxic form called Nitrate. That means you will need to do lots and lots of daily WC to keep these toxins at a safe level. How soon can you get a test kit? It will help you see what's going on chemically in your tank and when you need to do a WC!
