Make insert module add uploaded images to media library automatically
Instead of using the Insert module, use the Media module's WYSIWYG integration. This adds a button to the WYSIWYG toolbar which allows you to choose an item from the Media library. You can also upload a new media item which adds it to the library and selects it to be inserted into the WYSIWYG editor. The link above explains how to set it up. Make sure you follow all the steps. You have to enabled this functionality in both the WYSIWYG profile and the text format to get it working properly.

Also, check out this great video on Media for some more information.