My wife's affair??

he guy was supposed to be my "best friend". For 10 or 11 years they had an affair (even in my own bed and my son's bed). I never caught them, she finally told me about it and said she loved me and would never do it again and will never see or talk to this man again, should I forgive her, and how can I ever get my trust back, and get this knife I feel is sticking in my back out??? how long before the pain goes away, because I don't even want to live anymore, it hurts so bad.*
The guy's got an a** kicking when I see him, but should I trust her again?

Turns out my Mom told me later on after everything settled down that she and my sister had known my wife was cheating and with whom and for how long. I was livid at her for letting me go through so much misery when if she had said something I would have checked it out and divorced that woman instead of trying to make it work for so long?