How to forgive a cheater and gain trust.

About a month ago I found out that my boyfriend of 7 years, who I also live with and raise our two children with, has been cheating with a married woman. They both say they didn't have sex or see each other, just talked on the phone and texted a lot. I decided to stay because this is the first time he's ever done anything like this and I honestly love him and know I can forgive. But How? How do I get past always wondering what he's doing or talking to and finally be able to trust him again? What do we do?