Sharepoint_Config - Transactional LOG Full

Anyone knows why sharepoint_config transactional log is grow up everytime and goes to a FULL state fast.

I´ve following this script, and for the moment the log is growing down, but in 15 days more or less, the log goes to 15 GB, even the sharepoint doesn´t have almost nothing new or changed.

###SCRIPT#####
 
USE SharePoint_Config
GO
-- Truncate the log by changing the database recovery model to SIMPLE.
ALTER DATABASE SharePoint_Config
SET RECOVERY SIMPLE;
GO
-- Shrink the truncated log file to 1 MB.
DBCC SHRINKFILE (SharePoint_Config_log, 1);  -- here 2 is the file ID for trasaction log file,you can also mention the log file name (dbname_log)
GO
-- Reset the database recovery model.
ALTER DATABASE SharePoint_Config
SET RECOVERY FULL;
GO

#######################################################

How to fix this ?

Thanks,
Leandro