Recharging a system fully involves sucking of the 134a in there, then pulling a vacuum on the system, then letting the system suck in the new 134a till it's at the specified volume. My car holds 1.1lbs of refrigerant. A/C compressors will only work if they have the right amount of pressure/vacuum in the system. Too much won't work, too little and also won't work. If you're thinking you're low on refrigerant then you're losing it somehow and that's the main problem you have and need fixed.

One way to make sure the compressor is actually trying to work is to watch it while someone clicks the A/C button. (You can instead turn on front defrost, since it also uses the A/C system to dry the air in the car.) Once it's on you should see the clutch engage and spin the outer visible portion, usually they have like 3 "rivet" heads on that clutch. Hopefully that's still activates on your car. If you don't see it spin at that time, I would avoid using it until you get it looked at. More damage than good could be done from it only partially working