I have been using ubuntu 12.04 on my system for a long time. Suddenly the system has become too slow and cpu utlization is always above 80%. I have attached the screenshots which displays the usage at a specific time.
You have many google extentions enabled, tabs or windows and firefox as well You may have to watch why Chrome is using so much memory.
But I think you should shrink your swap. You have 3.8 memory installed and your swap is 3.8 gb.
If your swap is encrypted, then follow this guide: http://webcache.googleusercontent.com/search?q=cache%3awww.logilab.org/blogentry/29155&hl=en&tbo=d&strip=1
Edit: I think your CPU is just fine. Your ram is running out of space. Edit 2: Backup your chrome data and install one fresh. However if you have too many apps running with your chrome, I'd check how to backup them properly before anything else.