I am going through a similar situation.

After fighting every few months for 2.5 years about HER and me making myself think I had jealousy issues, it turns out I was right THE WHOLE TIME. They were talking about sex, had a make out session, went to lunch, went to a movie, he tired to get in her pants several times.

My advice? Where there is smoke, there is fire. If he had an ex and you felt jealous that would be one thing. The fat that they've communicated and he wasn't upfront about it speaks volumes. Let me guess.. he didn't tell you for fear of YOUR reaction?

Yep. sounds about right