frost problem

My 99 sunfire has been frosting on the inside of my windshield and back window. I've also had a problem with the windows fogging up a lot. When I'm in a large parking lot I've been looking to see if other cars had fogged under the same conditions, and I'm usually the only one. I noticed when I opened my door after our last snow storm that the snow was all in around the hinges and perimiter of my doors. I was wondering if that was part of the problem. Any suggestions would be great. Thank you!

If it does that when you start up your car its your heater core..

door seals