Am I a fool, what should I do now...

Long story short.. The man of my dreams has been in my life as a great dad and man for over 10 years.. 4 years ago, 4 weeks before we were to marry, I found out he was cheating physically with a co-worker.. We did therapy, we told her to leave us alone, his boss backed my wish and had her transfered to help us out.. We made it through the troubles.. ( He even called every family member and told them why the wedding was off).. Our family has been great since then.. I thought.. My oldest son, finally broke down and told me he was scaried to tell but he knew dad had another hidden cellphone.. I asked, never said who told me, but asked if it was true. It was and it was with the same lady again.. She called his work and the "phone sex" was all it was.. Ya right I know.. We both agreed last time that if it happened again, the person would leave and so I packed his bags and sent him to his mom's.. He cried, said he was sorry, called his counselor.. But now what.. What should I do.. I'm going to get my own counselor to heal myself, but how long should I ask him to be gone? How should I ever tust him again? Am I being stupid? He says he's scaried and that he doesn't understand why we are so great , never fighting, always loving and laughing. He doesn't know why he did it.. Is this possible? Could he be telling the truth and maybe help will help? He wants to come home, but I told him maybe after a month of counseling, but am I being the fool? Can anyone give me some answers or help.. Can any man out there please explain why a man who has a wonderful family, a loving women (as he says) do this? Please ... I feel lost, I love my family, I love my man, and I want him to love himself.. But how far do I help him achieve this? How far do I stand by his side? When is enough enough... Please help with some advice if you can... Thank you