Massive stuttering issue

There's never a problem when I enter the game, but when I enter a game mode like Ultimate Team or Clubs, the game drops to 4-5 FPS, and this continues even when I return to the main menu. Sometimes it doesn't drop, and I enter a match and it's playing smoothly, but by the end of the first half, it's back to 2-3 FPS, and I'm forced to lose matches I've won. I've tried everything with the game settings, but it never works. My computer isn't one that won't run the game, and when this specific problem isn't happening, I get very high FPS.