Furnace blowing cold air
You should call an experienced HVAC contractor.

It sounds like one of the safeties on your furnace has failed and it is not initiating or detecting the flame properly (I am guessing you have gas, propane, or oil). So it begins to work, cannot initiate or detect the flame so it fails and it may just leave the fan running when it fails.

A service call will be worth it when you are warm again.

Good luck!