Having fps drops during encounters BG's/raid's

Im starting to have massive fps drops whenever i join bg or starting any encounter in Raids and pvp, making it unplayable, i never used to have that problems in my years on this server, tried to set settings lower but never helped. Then i decided to delete the game and download it from scratch, and it worked, for a day and then it started again with the freezes in any encounters. I hope anyone have any suggestions about my situation, or even know how to fix this