So, my head gasket was leaking, so I put in some Bar's Leaks and now it doesn't leak. During the process my heater blew hot air the whole time. But, the directions said to leave the radiator cap off and the drain open over night. So I did that, filled it up in the morning, went off to work, but now I have no heat. What happened?

the stop leak has clogged up your heater core....

or u have an air pocket in ur heater core which is possible