hvac heating

My heating system works fine on the drivers side,but blows cold on the riders side,It works only if i put it on floor heat and use the recycle mode,Its very cold in wisconsin,so the windsheild soon fogs up,and i have to put it back on defrost,then the air blowws outside air into the passenger side.,And the passenger "ME" freezes "ALMOST" to death.It feels like its blowing in from the door,but i don't see any thing wrong with the door seal.and blows cold at my feet as well.