Help understanding odd framerates

[WrigleyPlaysPC]

Okay, so my rig is capable of pretty much any game, It plays Bioshock Infinite at high with 60 fps, BF4 singleplayer high 60 fps, COD AW Singleplayer High 60 FPS.

AMD Athlon ii x4 750k @stock clock of 3.4 GHz
Hyper 212 evo CPU cooler
4 GB Kingston HyperX 1333 Mhz DDR3
MSI a75ma-e35 FM2 MOBO
7770 Ghz Edition Powercolor 1 GB
CS430 Corsair 430w PSU
128 GB Sandisk SSD
500 GB Western Digital Blue
Windows 7 64 Bit

Here is my problem though, in BF4, and COD Multiplayer no matter how low I set the settings, I get occasional stutters and about 38 fps, no matter how high I set the settings (With the exception of Ultra), I still get about 38 fps and occasional stutters. The framerate doesn't seem to change. But on single player games I have no problem playing games at a smooth 60+ FPS. This problem doesn't happen with CS: GO, TF2, or any other multiplayer game. Would upgrading to 8 GBs of 1600 Mhz RAM do the trick? Also, after about 20 minutes of playing in COD, my framerate goes up to the max FPS of 91. But I still get occasional stutters when there are explosions or when I almost die, which ruins the point of the game. So, if you guys have any suggestions please do tell. Thanks!

 

[WrigleyPlaysPC]

Now I have noticed the singleplayer campaigns in both of those games are also stuttering. I get 60 fps for 2 or 3 seconds, and then a 5 second freeze, only to go back up to 60 even on the lowest settings. Could it be my power supply? RAM? CPU? I honestly don't have any idea.