(Before Info): Never Happend Before. Does this on all versions of minecraft. Doesnt do on other games.

(Info): Whenever I log onto Minecraft and turn on FullScreen, it shows on both monitors and its annoying whenever Im trying to watch a movie or video on my other monitor. Also, Main Display has Cursor but doesnt update screen. Second Monitor has no cursor and updates like it normally should. (I want to play on Main Screen). I FullScreen starting on the Main Monitor but if I FullScreen starting on my Second Monitor everything before still applies but the monitors are switched. (No Cursor on Main but does Update Screen etc.). 

Please Help!

Edit: After trying to take a screenshot it only shows the monitor that it fullscreened in and acts like the second is normal.