How Can I Cure My Foggy Aquarium?

Alrighty I have a 10 gallon fish tank with 2 one inch goldfish. The aquarium is quite foggy, now yes I have let it run for 2 months before I got any fish, the water was crystal clear for about I don't know 3-4 months once the fish were in it. All of a sudden within about a week the water got foggy 2 months later its still foggy; I tried using a supplement and nothing the only thing I can think of that caused it is I was a couple days behind on my water change at one point which actually was around the time it started fogging up. (Note I do a water change once a week. Also note I'm sick of using chemicals it can't be any good for my fish) Any ideas on how to fix this problem?