My Battlefield 3 used to run smoothly... Not anymore?

My BF3 once ran perfectly until today. When I launched the game, everything started to lag a lot! It's impossible to play. Before, i had my frames per second up to 60 and now its down to 10 - 15. Help! My specs: Windows 7 64-bit Intel Core i7-3610QM 8 CPUs 3.2GHz (Turbospeed 2.0) 8 GB RAM Nvidia Geforce GT 650m