boyfriend answering internet sex ads "for fun"

Hello,

I need some advice. I caught my boyfriend of 11 months responding to internet sex ads on Craigslist. He admits it is wrong, has apologized, and says it was just to pass time when he was looking for a job (he has one now) and that he'd never actually follow through on it. I have a hard time believing him. I have been checked for any STDs just for peace of mind. I think even if he didn't follow through, it was only a matter of time. He swears he'll never do it again and is begging for my forgiveness.

I am in my late thirties and am not naive. I fear this is some kind of compulsion. Except for this, he has been wonderful and it seemed like I finally found the love of my life. Now I'm devastated. Anyone have any experience or advice?