when i step on the brakes, i noticed that the pedal is getting lower and lower to the floor. what is causing this problem? any thoughts or comments would be appreciated

Do you mean that if you hold your foot on the brake the pedal seems to fade or keep going down? If so then probably a bad master cylinder.

Bleed the master cyclinder, then bleed at the wheels, farthest from the master cylinder first. If the problem is mechanical rather than hydraulic go to a parking lot and make several stops from reverse and it will adjust the brakes on the rear wheels.

when i step on the brakes, i noticed that the pedal is getting lower and lower to the floor. what is causing this problem? any thoughts or comments would be appreciated
In the future please post year make and model for ease of advice, makes sense, no?

If your car has drum brakes on the back, the self adjusters could be stuck. They may not adjust anymore. Its a more common problem with cars over 10 years old.