[TYPO3] Problem with caches

[Fred]

Hello,
I have a serious problem with my cache on my Typo3 websites.
Last monday I discovered that my database was about 90mo, after I cleard 
all caches it was about 20mo.
I checked and quite all the pages are set with "cache = 5mn".
I tried to set this on my main template :
config.cache_period = 180
config.cache_clearAtMidnight = 1
And this on the TS of the root page : TCEMAIN.clearCacheCmd = all
But it didn't seemed to work.

Does anyone has an idea of how to prevent this or how to empty those 
cache automatically ?

Thanks !