Actually, there is always 'mind pollution' going on, from TV, Radio, other people. (I've been a sensitive all my life). On top of this already thick grid of interference, it seems those bent on control of others have developed weapons of mind control that utilize our cell phones and TV's to 'leak in' manipulative thoughts.
Happily for you, you are aware of the outside interference (many aren't), and you still rule your mind. There are lot's of things you can do to short circuit all this interference. 'EFT' (
www.emofree.com) is very helpful, as are many other focusing and mind control techniques. I believe we are quite able to block out mental intrusions with a bit of training and practice.