Problems with the trash
It's possible that there are hidden files in your Trash that are not being removed for some reason and are constantly being "deleted". If you are ABSOLUTELY sure there is nothing in your Trash you may want to recover, you have two options.

Secure Empty Trash:


Right (CMD) click your Trash
Press and hold CMD, you will notice "Empty Trash" changes to "Secure Empty Trash"
Click "Secure Empty Trash"


This forces Finder to remove files that may otherwise be stubborn. It may take a while depending on how many files need to be deleted as the reference to the data is not only deleted, but the addresses the data is stored at (on your disk) is also zeroed out. Be wary of doing this with a Solid State drive as it will shorten the life of your drive (generally only by a small fraction, but caution should still be taken). If you have a Solid State (or Fusion) drive, I would recommend the following instead:

Brute Force Erase:


Open "Terminal"
If you have altered your Terminal settings, type cd ~ and hit Return
Type sudo rm -rf .Trash and hit Return
Enter your password


Terminal will remove the .Trash folder that stores everything in your Trash. This folder will be rebuilt by OS X as needed. This doesn't securely erase your data (by overwriting with zeroes) and thus is safe for use on SSDs and Fusion Drives. You can also use this if "Secure Erase" fails for some reason.

As @patrix notes, this will not remove anything from your Trash that was originally stored on an external drive as each drive has its own .Trash folder. If you have multiple user accounts, this will also not remove anything that another user has Trashed as each user has their own .Trash folder too.

As a precautionary measure, I would then verify your disk in Disk Utility (in case some data tables have been corrupted) and repair if necessary.