Confused on what to do

I just caught my husband answering a post on craigslist for a Hook up.... He basically replyed to the post, and they sent a reply to go to another site to view pics etc...and he wrote back "let's have some fun soon". The post wound up being a spammer anyway but he had no way of knowing that when he set out. He said he had no intention on doing anything (which I do not believe). And that he was curious...why he went there, and he was stupid for replying. He is begging me to forgive him, saying he will make it up to me for the rest of his life. He;d go to therapy....I don't believe him, I am a bit smarter than that. after all I caught him right. The problem for me is is that we were in a seemingly perfect relationship and this just blindsided me. If we had a rocky one , I'd more or less expect this crap.
Help

Good for you follow your gut instinct, deception does not belong in any relationship. Are there reasons, if you look back, for this type of behavior? Please keep talking only when you feel like it. Take care of you.

April

If he did it on craigslist he did it on other sites to. My husband was and still is meeting this woman on all the site and that's sick to me. Please try to stay strong and keep looking trust me you will find what you are looking for. I never thought that my husband would act the way he do and the things i read that he say to them omg.