Modern warfare reflex problem?

Why is it that my guy takes only about 3 bullets to kill but everyone else is like the friggin terminator and it takes a whole round and a half of machine gun fire to kill them. I'm a staff sgt. 2 or whatever the hell but i die in 2 seconds flat. I might as well be a friggin old lady instead. In fact i think an old lady can take more bullets then my guy. I think my guy is more worried about his hair then his life. Lol.