Large Premier Pro sessions saving and loading very slow if at all. Plenty of hd space and 12 g ram

I'm working on a music video. Everything was fine with loading and saving until I got about 10 video tracks rolling. Suddenly the session files jumped from 36 to 65 to 400 meg 1.2 and then 2 gig. These were in succesive numbered saves with maybe 10-20 minutes between them. Then the next file I tried to save took an hour and a half and still didn't save right and used 35 gigs of hard disk space trying to save the file which I got back on the hard drive after rebooting. I can't load the last session back up it just hangs. I'm stuck!