a/c problems!!!

[DBrown]

my air only blows cool air from the driver side and only when set to mid level air (not the upper or lower vents), they blow hot air in from the outside i guess. my a/c refrigerant seems to be just fine but once the air gets to the ductwork something happens and hot air is let in. they all blow hot except the one now. it started with the foot level vents and rear and now the middle and passenger sides are warm as well. when i turn the thumb control knob from 3blue dots to the hot side it does get much hotter though, so i guess the knob is working. any advice? i think a damper or ductwork is messed up??