Sex addict, what to do?

Been married for 15 years, and slept around in the entrie time. I like very much my wife and cannot imagine my life without her. But, I cannot resist my impulses and craving for sex. No children, but my wife would like to have a child and I am running out of excuse. It is a devastating dillema, being honest with her by telling her the truth and breaking my marriage, or trying hard to stop it without telling her anything or carry on in the same way. Any help and idea is most wlecome.