Is my husband obsessed?

[askalot]

My husband has been on facebook for about more than 6 months now and he reconnected with a lot of his highschool friends & one of them he developed an online relationship(as what i call it) after i found out that they were exchanging explicit chats thru this fb site and after the first blow-up, he told me that it was all a game in front of all these audience in fb, telling me that it was all a show(as he calls it "a hurtful joke'). It nearly destroyed our marriage so we had a long confrontation together with my inlaws too. After that, another blow-up came when i found out that they had created another account so they can continue with their games(huh???); I called & sent a text to the woman(nothing really mean), and warned my husband about all these madness. He apologize. things got settled for a while. we went on vacation with kids. had fun. after that i found out that he sent a long email to his friend again telling her in detail about our vacation even telling her that we are having marital relations again w/c i think is very personal. He also emailed her earlier before our vacation that their FB game should stop & he promised me that he would not flirt anymore with her FB friend but just be "friends." Now i found out lately that he created an account in twitter where his "friend" is also using. Another of his FB friends found out about it & asked him what he's doing in twitter & he replies "I have no freakin idea."
Please help me. what is going on. what should i do? we have been very nice & attentive to each other lately & I know that we love each other. He is making me feel that he really loves me. but what about his cyber obsession. is this something i need to be worried about?