Lag Spikes

When I first starting playing Civ 5 on my laptop, it barely lagged at all. After taking a long hiatus from the game, I went back to it and found it to be horribly laggy, especially in the late game. I tried updating my graphics drivers, but that (surprisingly) made the game even laggier and it messed up the textures when playing in dx11, so I reverted to the old ones. The game will go between 30 fps to 8 fps (or worse) every few seconds, and later in the game I have to zoom when clicking units or it won't register that I selected it. I have tried almost everything, from disabling windows aero themes to lowering gfx settings to trying popular "game boosters," but the all seem to have minimal effect. Any ideas on what can be causing these horrible lag spikes?

System Specs:
Core i3
HD graphics 3000
6 GB ram
Windows 7 64 bit

EDIT: changing the corethreading (or whatever it is) to 0 fixed the unresponsiveness when clicking, but the lag still remains. :(