When you say “stinky water”, do you mean sulfur smell? Does all the water stink all the time, hot and cold? When you add bleach, are you shocking the water well itself or adding in the filter housing or water heater?
If you have sulfur odor but not that bad, just enough to make guests cringe, get yourself an aerator, which is about the size of a check valve, and install it as early as possible in the line when it comes out of the ground. Most plumbing supply stores carry these and they’re pretty cheap.
Hydrogen sulfide or H2S is a gas, and you can’t catch a gas in a filter no matter how many you have. It has to be oxidized, or changed to a solid, to be caught in a filter. Bleach oxidizes the sulfide but so will oxygen, and that’s where the aerator comes into play. Oxygen strips electrons from the H2S, drops the “S” off and jumps on to make a new H2O molecule. The sulfur then becomes a solid so your filters will catch it.
In the olden days, a windmill pumped water into a cistern where atmospheric oxygen would take care of hydrogen sulfide within a few seconds. Today, the system is closed so you have to get oxygen into the line artificially.
Hydrogen peroxide will also break down into water and oxygen and is much cleaner than bleach, which produces carcinogens called “trihalomethanes” not to mention that it smells bad, tastes bad and is very corrosive. Typically, around here anyway, folks will shock the well with bleach once or twice a year, then run all the bleach out but that would be for bacteria infestation. Every three weeks is a bit extreme.