How Do I Get Over What My Boyfriend Did While We Were Temporarily Not Together?

I have been in a relationship with someone committedly for almost 3 years. I should say in and out of a relationship for almost 3 years. I have always remained faithful even though we went through periods of time where we considered ourselves ‘not together’. We both eventually started dating other people, me not as exclusively of course, as he dated with his co-worker. He ended up sleeping with her even though he was still hanging around me as ‘just friends’.

I could barely bring myself to kiss someone so it is extremely difficult for me to understand how he could let himself be intimate with someone other than me. We have been back together for a while and on occasion I think about the brief relationship he had with this other woman. Over this Christmas holiday we went to his sister’s house to visit for a day trip. Well, I walk into her house and remember that my boyfriend had sex with this woman in this house.

Let’s just say I had a private panic attack. The kind where you just look around breathless wondering which surface, which room, did that moment happen when he let himself be with someone other than me, since me. My boyfriend is 8 years older than me, has had more than triple the amount of partners as me, and my first love. I was 18 and he was 26.

What makes things worse is we are expecting a little girl in May 2011 and I can’t get over these feelings of deceit. I want to get over them for our little one coming.