I'd found Philippe was cheating on me and I was angry and hurt.
发觉菲利普对我不忠后，我又气愤又伤心。

I have an affair with my secretary.
我和我的秘书有暧昧关系。

I think my spouse may be unfaithful to me.
我觉得我的爱人/配偶可能不忠于我。

At the very least, my heart has been derailed.
至少，我的心已经出轨了。

We also hear the expression love-rat used quite often in popular newspapers.
“爱情老鼠”（爱情骗子，指那些经常在恋人背后出轨的人）这个表达也经常出现在那些通俗小报上。

I'm sure he's got another woman. 
我确信他有了第三者.

Arthur himself has been portrayed as a weak cuckold.
亚瑟王本人被描绘成一个被人戴绿帽子的软弱之人。

After Wenzhang, Chenhe became another notorious two-timer in the entertainment world.
继文章之后，陈赫成为娱乐圈另一位臭名昭著的脚踩两只船的明星。

She was a third person in a relationship for about 11 months.
她做第三者已经有11个月了。