Download Shrinking

I bought Battlefield 3 quite a while ago, but i have not been able to download it. Whenever my download reaches around 5/6GB (i cant say exactly) it seems to return to around 4GB. I can leave the download going for a while and come back with a smaller file. Even if i go into the Origin Games folder and check the size of the Battlefield 3 folder it says it is the size the download manager says, meaning the actually folder is shrinking.

my hard drive format is not FAT32, I saw that that can cause similar problems and checked.

my specs:

intel pentium dual core 3.2GHz

nvidia 640 asus 2gb edition

windows 7 professional 32-bit

thanks for any help 🙂 

(edit: if it helps i have downloaded games of this size on steam)