Without looking at your script it is hard to tell what is using up all the memory. You should know better: Do you have so much data that it would fill your RAM?

If not, could it be that you don't delete child processes correctly?

You could (if you are on linux or some other unixoide) type "ps -elf" repeatedly in a shell while the script runs to check if either one process gets too big or too many processes are created and are not removed.