I won't comment on the cheating, because there's no way to tell, from what you've written. But a good place to start is with the SSM book, if you haven't already read it. If you can get your wife to read it too, that's even better... Internalize the idea that "I will not stay in a sex-starved marriage forever." Having kids makes this a much more difficult problem (I know; I have kids too).
