My wife seems so sensitive about everything. What can I do to avoid divorce?

My wife and I just had a huge argument and we may be finished. We have a young son, whom we both love. The issue seems to be that she gets so angry about almost anything I say. An example is she asked me if I wanted something to eat and I said no because we already planned on having something else. She started raising her voice and we had a BIG fight. This seems to be our situation more often than not--little things like this set her off. Admittedly, I am grumpy from time to time, but do I deserve this? I tell her that this doesn't work for me. The best thing I can do is avoid the fight, but she will sulk about it for hours, without realizing she is getting angry.