Thanks for your comments, everyone. To answer some of the points that have come up, the 3 sites that I?ve found her on have all been under different usernames. I met her on a free site and the other two were subscription.
What prompted me to hide my profile was a jocular comment I made early on in the relationship about being on the site and still receiving mails. She went a bit quiet for the next day or so and I found out that my comment had been taken badly, so to show her that I wasn?t a player I hid my profile there and then, and told her so. I suspect that I should have had The Talk, but her reaction to this and the way our relationship was going made me think it wasn?t necessary and may upset her.
There was a time after a couple of months where she was very evasive about what she?s been doing one day. If not seeing each other we?d speak on the phone two or three times a day, so this made me ask her ?what?s wrong? and she got defensive. It was then that I looked to see if she?d hidden the profile on the site on which we met, and I suppose I was quite ok with her logging in every 3 weeks or so to, as I guessed, message anyone to say she was in a relationship and clear out the inbox. So yes Time, there was a possible underlying problem which was the real trigger, and then another trigger which led to me looking for her on other sites.
Zany, she did say that the sites were just a bit of fun. However I suppose that I?d been looking for reassurance that nothing was going on, and did ask her if she was on other sites (knowing she was) and hoping she would come clean, that it was something innocent and therefore there was no breach of trust. However she denied it, which made the problem worse. My own fault. :) She was also quite assertive in telling me that I was making a mountain out of a molehill.
Loves, I wondered if she does just want the flattery and flirting, and there?s actually nothing more to it. Certainly this would be consistent with the way she acts and talks to me. However, my problem is now that she?s told porkies to cover it up, and this eats away at the trust. Having had two conversations about it, which both of us found distressing, have resulted in me nearly walking out and her persuading me to come back. So she knows that her continued presence on the sites upsets me, yet she continues to log in, supposedly unbeknown to me. At the very least she?s somewhat arrogant in ignoring my feelings!
So it?s a complicated situation, but certainly not so life changing as some on this board, to keep it in perspective. Thanks for all the comments so far, and more are welcomed!