in order to love his wife, a man must have affairs.

Here are a couple of ideas.

After having an affair with his boss, a jaded accountant discovers a new found love for his wife, but to keep the spark in his marriage alive, he must become a serial cheater.?

Or

After having an affair with his boss, a jaded accountant discovers a new found love for his wife, but to keep the spark in his marriage alive, must he become a serial cheater??

Re: Tony Edward's logline:
I think it does the job. The paradoxical dilemma the philandering man discovers IS the dramatic problem. That's what happens in relationships: people find themselves having to juggle conflicting desires and demands. The conflict is primarily internal: the guy is his own worst enemy, his own antagonist.

Yep... That was a tad harsh (one of those days..).

The concept does present the potential for an interesting dilemma -- but as others have said, focus on being specific with your lead character and what they HAVE to do. Below is really only an extension of your concept and not really great as a logline, but anywho:

"After having an affair with his boss, a jaded accountant discovers a new found love for his wife, but to keep the spark in his marriage alive must become a serial cheater."

Best of luck.