For the frequency of water changes, it kind of depends on your water perameters, but I like to do 25% weekly. I use a gravel vaccum, and it is great because it sucks up all the junk in the gravel, but doesn't suck up the gravel itself. Then you can clean and water change at the same time. If you don't have one, ask your lfs. They should be able to help you out. Conditioner is great for many reasons, but the most important is that it removes chlorine, which will kill your fish and wipe out your beneficial bacteria colonies. When doing water changes, also remember to match the temperature of the fresh water to that in the tank.
With your gourami, pregnant isn't the correct term here. Gouramis are egg layers. The male builds a bubble nest at the top of the water and the female deposits the eggs there, then he fertilizes them, then babies. Please note that there are other steps in there to getting them to mate. You should really post the breeding questions the breeding section as I have never bred them and understand that it is quite complicated...not like guppies and such that just keep popping them out. If you don't get a male, the female will release her eggs and no biggie.
What size is your tank and what do you have in there? How long has it been running? Do you have the proper tests to determine what your ammonia, nitrITE, nitrATE? Is your tank cycled?
