Not only could there be a clog somewhere in the system, but your vaccuum controls may not be routing the air appropriately. There is a switch attached to your A/C lever that will make the vacuum doors underneath the dash move. Check, when the A/C is blowing, if you are feeling air come out underneath (near your feet) or out of the defroster. If so then you are not routing all your air through your A/C vents.
Also, there is a switch that actually moderates the flow of electricity to your blower motor and thus controls the blower speed. If this switch is bad it could be stuck on a lower speed.
Perhaps all of these things plus what other people have said is causing the lack of "hair blowing". HOpe this helps!