In the first instance, please go to Support in the top right of your admin CP and address any items that are showing there. If there are old tables that need to be removed, this will tell you. Secondly, you need to ensure you are logging only errors that are needed. As mentioned above, this would usually be logging only level 3 and above.
Another item to check would be to go to your system logs within the support area, and ensure you dont have any system errors being logged over and over, which may be causing tables to fill up.
If all else fails, please update your access details on file, and I can take a look to see if there is anything causing you obvious issues there that I can see. You can see how to update your access details here
Https://invisioncommunity.com/4guides/welcome/getting-support-r292/#access