I'm worried about my tank!?

It is cloudy and I'm worried about my tetras, cherry barbs albino cherry barbs, guppies and male flamming dwarf gourami in my 40 gal, I did 8 gal changes yesterday and the day before. I guess it got a little better but i don't want anything to happen to them cuz I'm obsessed with them for some reason and don't want to start over! Will the water clear up on it's own? Should I do more water changes? Do I have to buy stuff? I don't no wat kind of filter I have but when I got it from my neighbor, it was for a 55 gal and it's pretty big and has to sides so it has to filter cartridges if that helps. And a heater for the appropriate size gallon. I think it might be cuz I have to much fish, but I'm working on getting rid of all my guppies. I cansee thru the tank on the front and back but Barely can see thru the sides to the other side. So wat are some reasons it's cloudy