Committing Adultery - Need help to stop?

I do love my partner, but I find that I get a kick out of having initmate relations with someone else, especially if they too are married or in a relation. What is strange is that when I try to perform with my partner, it takes time for me to reach , and more often than not, it doesn't happen. However, with other women, I find that I come earlier than I want to. This may be entirley psychological and this is a sick and dirty habit I want to get rid of. Has anyone been in a similar situation and what tools did you use to stop this horrbible betrayal? Regards