[SWHouston]

Your post implies that you live in an Apartment. They are notorious about sharing problems like that.

I hate to recommend a dedicated Insecticide in any case, but you might try it just in the areas that are most prone to allow a contamination. Those being at any door which leads out to a common passage. Any pipes which come up through the floor, or wall. Like under your kitchen/bathroom sinks, and any Natural Gas outlets you may have.

Addressing these select areas should help, but, you can always have a complete decontamination done on your residence.