Hi Amelbourne boy, so glad you posted here and welcome.
It isnt easy posting opinions here sometimes but we are trying to help people like you. In an ideal world we'd wait until much more information is available.
My gut feeling is you are suffering a very common form of fantasy. And such fantasies and the effects of them if pursued, would crash down heavily upon you and the people around you. Then there could be the regrets.
You have seemingly a very good relationship of trust and companionship. As you say- its wonderful. But you now think there is something missing due to talking to this third person. This third person has filled a small gap inside you, a gap your current partner cannot fill simply due to his personality. There is, in my view, nothing wrong about this, it often occurs, but....theoretically if you left your partner for someone else due to "what your current partner doesnt have" you will find any new partner will, down the track, also have parts missing that will leave you longing for - and the cycle continues.
Having said that, try a few things. Firstly dont under any circumstance go looking for company on the web. That is a trap and a no no. It is in fact breaching your trust you have with your partner and highlighting you are searching for "everything" in life that you dont have. A display of lack of content. Secondly spice up you relationship with your partner. As the rest of your life is settled- try thinking of some new holidays or other interests together. 9 years and it might be time to throw in some spark.
I watche don telly once that a psychiatrist had a young beautiful patient that he found extremely attractive. She was single and he was married. It seemed she was everything his wife wasnt in terms of beauty. But he refrained from stepping over the line because a/ his professionalism b/ his commitments to his wife and c/ beauty is only skin deep. He had to constantly remind himself of these 3 principles every session. After many session he realised these principles were even more relevant as he got to know his patient more and more. In the end, with far more knowledge of the patients personality, values, lifestyle etc etc he was relieved that he wasnt tempted.
The lolly shop of life can be a delusional one. Take care.