As everyone say here... get rid of the moisture. Mold needs two things to grow: moisture levels at or above 60% and organic matter it feeds on. You use the basement as a bedroom, therefore you can't eliminate all the organic matter. Your only option is to keep moisture levels down by running a dehumidifier. Other than that, no matter how much you clean, (and how toxic are the substances used to do it) the mold will just keep coming back. I would also recommend you get rid of the carpet, as even the driest basement has moisture from the ground consistently seeping through the concrete. The carpet soaks it and favors mold growth as well. It is also a good idea to check the insulation behind the drywall. If it is fiberglass and it is moist, it will also grow mold and lose all of its R-value. In other words, get rid of the moisture and don't have anything that can soak up moisture against concrete floor or walls. I am sorry to inform but there is no cheap fix for the problem. What is already contaminated by mold, has to come off. Besides the smell, even the non toxic forms of mold are know to cause breathing problems and trigger allergy symptoms. Not a good thing to have around.