FPS Lag...

I've owned Alienware computers for the past couple years, and just back in September, I got a new one (my old one broke.). I just bought the new black ops 3 DLC Awakening and I just realised, my FPS is complete . My FPS average is 30 #firstworldproblems. The game is pretty much too laggy to play. The first day I got my new Alienware, it ran like a champ. Now cs go is running 30fps when it should be running 250 like it used to do. I bought the Alienware computer for a reason, and that was high performance. Not totally frame rate. I want to post this thread to see if any of you guys can help, because believe me, I've tried a lot to fix the frame rate, and nothing works. My specs are below, well, basic specs. I hope you guys or this forum can help, and if you can, please get back to me ASAP. Thanks! :)