I have a hd 7770 1gb and a fx 4100 previously me performance seemed decent, sometimes i could even play on high pre set. However now that is impossible, even on medium i get like 40 fps and stuttering, cpu usage is always full basically, just bouncing about between 90 and 100 and gpu is at 70. Its not temps, I have already checked and mine should be fine. Any ideas, thanks in advance.
It's hard to answer your questions w/o you giving a bit more information. What resolution are you playing at? Are you overclocking your CPU? Did you recently up your resolution? If you went for a lower res monitor to a 1080p or higher monitor you will take a small performance hit. Are you basing your performance on online play or campaign?
I will answer your questions based on the assumption you are playing at 1080p and that you are not overclocking your CPU. The FX 4100 is honestly a pretty poor performer. Especially when you take BF3 online in which your CPU use will spike substantially. It honestly sounds to me like your performance is to be expected w/o overclocking as that 4100 will bottleneck even the 7770 to a slight degree.
I would say buy an aftermarket cooler and get the FX 4100 to around 4.5 ghz or so and this should give you a bit more performance. But don't expect to play on high settings anytime soon with that video card. After overclocking your CPU the only way to get more performance is to get a better video card. You should be able to play on medium with no AA w/o problems though.