mouse is the most important thing after skill and aim in any FPS.
get a new mouse. some people use Logitechs G-series, but IMO they're all metabolic end product. get a razer, either a diamondback (laser) or deathadder (optical). I use a deathadder for almost a year, it cost me around 30 euros, and it's the best *loving* mouse ever.
mouse surface is also very important. I use something a mousepad supporting my wrists, it is very comfortable:

you can always go for your Icemats and Goliaths and metabolic end product but whatever.
as for keyboard, don't go for that famous G15. it's metabolic end product. too expensive, not really helping. you can either get a keyboard with low-profile buttons (like in laptops/netbooks aye), or a high-profile classic keyboard. Personally I'd suggest the high-button ones, low-profile just feel unsure, I never know if I've pressed that key or not :P I have some cheap Tracer metabolic end product, 10 euros, works like a charm and has no unneeded metabolic end product. also wrist support for your keyboard is a must.