You sound as if you are emotionally exhausted.That's what stress does to people,it wears you out.
Sometimes we have to learn how to turn off the internal dialogue in our heads and just learn how to chill.The approach is different for everyone.
For some people that is a hobby or exercise,something that is just for relaxation alone.
Avoid caffeine,that can cause heart palpation's.Learn how to breath properly,during stress people tend to hold their breath and as a result do not get enough oxygen.That can lead to other physical problems ,which causes more stress.
Explain to your wife to be that you are having this difficulty and tell her to ignore your behavior as you are just taking it out on the person closest to you.. her.Sadly,that is what couples often do.
Being overwhelmed is natural.Know that you need to learn the tools of coping.It does not just happen,we need to work at it.
Here is a link I hope you find beneficial.
Discovery Health :: Eight Ways to Beat Stress