Hi, I got a 93 Chevy Lumina about 3 weeks ago, it had heat, now it just blows air....It's like it tries to blow warm air, but it never warms up. Could it be my heater core? Earlier i added some coolant, but after i put some in it i saw that it needed "special" coolant, could that've triggered my problem?

 

Fist thing to check is fluid level(sounds like you already did this), then check to see if the engine gets warm enough to produce heat(thermostat stuck open?), run it while checking the temperature of both heater hoses. If neither hose gets hot after 10 mins,check the upper rad hose to see if it is hot. If not, then its more than likely a thermostat stuck open.
If when checking the heater hoses, only 1 of them is hot, then the heater core is plugged and you either ned to replace it, or flush it out

 

okay, thanks ill check that