Minecraft Screen Freezing/Lag?

In Minecraft, every time i try to turn quickly or start sprinting/any sudden movement, my screen freezes almost as if i'm taking a screenshot. This is VERY frustrating since all i play is pvp. This started happening last night, any ideas? Also, for no reason my minecraft fps dropped nearly half than it is normally, i don't know why but it is kinda annoying, this is on all servers even single player. All help is needed, thanks.