External Screen/Fullscreen/Troubleshoot

OK so recently I had a small flat screen laying around and decided to hook it up to my Macbook pro. I have it connected and can drag other windows over and things like that. The purpose for this is that I do alot of research and need more window space to have multiple documents/windows open at a time to reference back and forth from. My problem is that I am a huge fan of full screen mode on my Macbook Pro, its basically all I use. When I have something on my external monitor, like a document/website/music/ whatever I am using it for and then swipe over to lets say safari or another program on my Macbook Pro I have open in full screenmode, the external monitor swipes with it into this gray blank screen. Is there a way to stop that from happening and to just keep whatever I dragged over onto the external screen and still be able to use my Macbook Pro as I normal would?

Thanks for your time,

Tim