Hi
After a long effort spend investigating why my db file became so large,
I found the problem.
We use SQLAPI to connect from a c++ application. It seems that even
though We only performs read queries on that connection,leaving it open
causes the problem.
I've also submitted this bug to SQLAPI support.

The workarround I have for now is reconnecting every X minuts.
This slows down considerably the growth of the db file.
Hope I helped anyone.
If anyone knows this bug or have a better solution or have anything
at all to say about this issue I'll be glad to here about it.
Thanks
-gili