It seems to be considered a single word.

Not sure if these are valid references, but:

1. https://answers.yahoo.com/question/index?qid=20091003034818A...

2. http://en.wikipedia.org/wiki/Contraction_(grammar)

The contraction "I'm" is only one word.

There are six words, but it isn't a proper sentence. That was the part that I immediately noticed.